ECONOMICS  OF 
ROAD   CONSTRUCTION 


BY 

HALBERT  POWERS  GILLETTE 


SECOND    EDITION 
SECOND  THOUSAND 


NEW    YORK 
THE    ENGINEERING    NEWS    PUBLISHING    COMPANY 

1908 


COPYRIGHT,  1901.  1906,  BY 
THE  ENGINEERING  NEWS  PUBLISHING  Co. 


CONTENTS 


Chap.  Page. 

I.     Historical   Review 1 

II.     Earth  Roads  and  Earthwork 3 

Profile  of  Cross-Section  of  Road 3 

Longitudinal  Profile 6 

Gutters  and  Drains 6 

Embankments   7 

Cost  of  Earthwork 8 

Surfacing 11 

Traction  and  Tractive  Power 13 

Location    15 

III.  Gravel   Roads 16 

IV.  Macadam  Roads 19 

What  Holds  Macadam  Together 19 

Quality  of  Stone 23 

Relative  Wearing  Powers  of  Stone 24 

Quarrying   T 25 

Drilling    26 

Dynamite    -. 27 

Crushing    27 

.       Hauling    29 

Spreading    30 

Rolling    31 

Sprinkling    .  . 32 

Quantity  and  Cost 32 

V.     Telford   Roads 38 

VI.     Repairs   and   Maintenance 40 

Continuous  vs.  Intermittent  System 40 

Sandstone  Macadam 41 

VII.     Suggested  Improvements  in  Existing  Road  Specifica- 
tions      44. 

Kind  and  Sizes  of  Broken  Stone 44 

Depth   of  Pavement 45 

Final  Surfacing 46 

Material  for  Embankments 47 

Thickness  and  Width  of  Pavement 47 

VIII.     Summary   and   Conclusion 48 


ILLUSTRATIONS 


Fig.  Page, 

1.  Standard    Cross-Section   for   Macadam    Roads,    Massa- 

chusetts  Highway   Commission,  -      4 

2.  Cross-Section  of  Road  with  Gentle  Curves  and  Shallow 

Ditches,       -  -      4 

3.  Macadam  Road  with  Deep  Ditches,     -  6 

4.  Macadam  Road  with  Shallow  Ditches,     -  -       7 

5.  Deep  Ditch  and  Culvert  Partially  Filled  with  Dirt  Wash- 

ings, -     10 

6.  Macadam  Road   on   Steep   Grade   with   Shallow  Paved 

Gutters,  11 

7.  Typical  Cross-Section  of  Macadam  Road,  as  Recommend- 

ed by  the  Author,       -  -     25 

8.  Macadam  Road  with   Shallow  Ditches,   after  Winter's 

Use,  29 

9.  Another  Example  of  Shallow  Ditches,     -         -         -         -     36 


ECONOMICS  OP  ROAD  CONSTRUCTION. 


Chapter  I. 


HISTORICAL  REVIEW. 

The  roads  of  the  Romans  were  built  at  enormous  cost,  probably 
not  less  than  $50,000  a  mile.  They  were  constructed  of  stone  laid 
in  mortar,  the  courses  aggregating  about  36  ins.  in  thickness.  No 
regard  was  paid  to  topography.  Hills  were  climbed  or  excavated, 
even  where  by  a  slight  deflection  they  could  have  been  avoided, 
and  drainage  ditches  seem  to  have  been  entirely  omitted.  It  was 
not  until  1764  that  Tresaguet,  a  French  engineer,  began  to  con- 
struct roads  upon  scientific  principles  by  using  small  broken  stone 
placed  upon  a  well-shaped  bed  of  larger  fragments  set  on  edge. 
The  same  type  of  road  was  later  introduced  into  England  by  Tel- 
ford  .about  1824,  and  roads  so  constructed  are  generally  known 
by  his  name. 

About  the  same  time,  or  possibly  a  little  earlier,  a  genius  ap- 
peared in  the  person  of  Macadam,  who  discovered  that  the  foun- 
dation course  of  large  stone  set  on  edge  was  unnecessary ;  and 
that,  provided  the  soil  was  well  drained,  a  bed  of  loose  broken 
stone  some  6  to  12  ins.  in  thickness  would  become  sufficiently 
bound  together  under  traffic  to  uphold  the  heaviest  of  wagon 
loads.  No  further  advance  in  the  science  of  road  construction 
occurred  until  the  invention  of  the  stone-crusher  and  the  intro- 
duction of  the  steam  road  roller,  both  within  recent  years. 

It  may  be  safely  said  that  half  the  controversies  between  engin- 
eers over  the  subject  of  road  construction  are  due  to  the  fact  that 
one  class  of  engineers  still  adheres  to  the  rules  of  Macadam  with- 
out recognizing  the  changes  wrought  by  the  steam  roller  and  the 
crusher.  The  broken  stone  road  of  to-day  is  quite  a  different 
structure  from  the  type  of  road  built  by  Macadam,  who  used  hand 
broken  stone  that  was  practically  uniform  in  size,  laid  in  the  road 
without  the  addition  of  a  binder  of  stone  dust  or  sand  and  left  to 
be  compacted  by  passing  wheels.  What  was  the  result?  The 
wheels  cut  ruts  in  the  loose  stone  until  the  soil  worked  up  from 
below,  while  the  action  of  the  wheels  powdered  and  broke  some  of 


2  EARTH    ROADS 

the  stone  until  the  voids  were  filled,  and  the  mass  became  packed, 
weighing  90%  to  95%  as  much  as  solid  stone.  In  this  process  it 
took  18  ins.  of  loose  broken  stone  to  make  12  ins.  of  macadam 
surface,  or  1.5  cu.  yds.  of  loose  stone  to  1  cu.  yd.  of  macadam.  To 
this  day  it  is  therefore  stated  in  every  text-book  known  to  the 
writer,  that  the  steam  roller  will  compress  loose  stone  one-third, 
or  that  6  ins.  will  roll  to  4  ins. ;  which  is  one  of  the  errors  that 
seems  never  to  be  contradicted. 

Rolled  as  roads  now  are  with  a  steam  roller,  no  such  compres- 
sion as  this  is  possible ;  although  in  cases  where  the  stone  is  placed 
upon  loose  unrolled  earth  sub-grade  some  stone  is  driven  into  the 
earth  and  lost,  which  has  led  many  engineers  to  believe  that  the 
roller  had  compressed  the  stone  33%,  or  even  more.  This  is  men- 
tioned as  but  one  of  the  errors  commonly  accepted  as  truth,  and 
one  that  is  in  a  measure  accountable  for  too  high  estimates  of  the 
amount  of  broken  stone  required  on  the  one  hand,  and  too  low  an 
estimate  of  screenings  on  the  other  hand.  The  true  shrinkage  will 
be  given  later. 

With  the  introduction  of  the  rock  crusher  came  a  large  amount 
of  stone  dust  or  screenings  (%-in.  diameter  and  less).  These  were 
at  first  rejected  as  being  worthless,  in  fact  detrimental  to  good 
road  construction,  but  some  one  with  more  brains  than  book-learn- 
ing tried  them,  and  found  that  they  made  the  road  bind  more 
quickly  and  gave  better  results  than  were  attained  by  following 
Macadam's  specifications.  The  use  of  a  binder  in  conjunction  with 
the  steam  roller  then  made  it  possible  to  build  a  good  road  in  a 
few  days,  where  formerly  it  had  taken  months ;  and  it  led  to  the 
building  of  "thin  roads,"  of  6  ins.  and  even  4  ins.  depth  of  road 
metal.  Such  a  radical  departure  from  precedent  was  and  still  is 
ridiculed  by  some  engineers,  but  common  sense  and  economy  seem 
now  to  be  winning  the  day. 

We  have  seen  the  thickness  of  broken  stone  roads  reduced  from 
the  36  ins.  of  the  Romans  to  the  18  ins.  of  Telford,  to  the  12  and 
even  the  6  ins.  of  Macadam,  to  the  6  and  in  some  cases  the  4  ins.  of 
to-day. 

The  recent  achievements  in  economic  road  construction  are  due 
entirely  to  three  factors:  (1)  Proper  drainage  and  rolling  of  the 
earth  foundation ;  (2)  The  use  of  machine  broken  and  screened 
stone  with  the  screenings  for  a  binder;  (3)  Thorough  consolida- 
tion with  a  steam  roller;  and  it  is  safe  to  say  that  an  economic 
road  cannot  be  built  unless  all  of  these  factors  enter  into  its  con- 
struction. There  is  yet  another  factor  that  up  to  the  present  has 


EARTH    ROADS  3 

•  9 

been  ignored  by  engineers ;  namely,  the  use  of  machines  for  grad- 
ing. Contractors  have  been,  and  are,  well  aware  of  the  great  econ- 
omy attending  the  use  of  drag  and  wheel  scrapers,  of  "road  ma-; 
chines ' '  and  Shuart  graders ;  but  the  cross-section  of  roads  de- 
signed by  engineers  is  usually  such  that  the  use  of  these  machines 
is  practically  impossible.  A  reference  to  the  reports  of  the  Massa- 
chusetts Highway  Commission  will  disclose  the  fact  that  about 
5,000  to  6,000  cu.  yds.  of  earth  excavation  are  made  per  mile  of 
road,  at  an  average  cost  of  about  33  cts,  per  cu.  yd. ;  wages  being 
$1.50  for  labor  and  $4.00  for  team  and  driver  for  nine  hours. 

It  can  be  positively  stated  that  both  the  amount  of  excavation 
and  its  cost  can  be  greatly  reduced,  and  probably  50%  saved,  sim- 
ply by  a  change  in  the  cross-section  of  the  road,  permitting  the  use 
of  scrapers,  and  by  a  change  in  specifications,  permitting  some 
vegetable  matter  in  the  embankment,  and  the  requirement  of  less 
labor  in  slicking,  or  "sandpapering,"  the  slopes  of  embankments, 
and  omission  of  sprinkling  and  rolling  during  construction. 

This  statement  will  become  more  clear  upon  perusal  of  the  next 
chapter. 


Chapter  II. 
EARTH  ROADS  AND  EARTHWORK. 

The  cheapest  in  first  cost  and  consequently  the  most  common 
form  of  road  is  one  made  entirely  of  earth,  properly  crowned  and 
rolled,  either  by  wheels,  or  by  rollers ;  and  in  any  case,  whatever 
may  be  the  paving  material,  the  cross-section  should  be  designed 
along  the  lines  now  to  be  described,  if  true  economy  in  construc- 
tion is  desired. 

PROFILE  OF  CROSS-SECTION  OF  ROAD.— It  is  too  prev- 
alent a  practice  to  design  a  uniform  cross-section  for  a  road, 
regardless  of  the  soil  of  which  it  is  made ;  regardless  of  the 
climatic  conditions,  and  the  drainage  area  that  the  ditches  must 
serve ;  regardless  of  the  inclination  or  slope  of  ditches,  and  regard- 
less of  side-hill  or  other  excavation.  As  an  introduction  to  the 
consideration  of  these  factors  present  practice  in  road  construc- 
tion will  be  discussed,  as  exemplified  by  the  standard  cross-section 
used  and  recommended  by  the  Massachusetts  Highway  Commis- 
sion, 


4  EARTH    ROADS 

The  ditches  are  commonly  made  3  ft.  deep,  1  ft.  wide  at  the  bot- 
tom, with  side  slopes  of  2  to  1,  as  shown  by  Fig-.  1.* 

This  great  depth  is  given  to  the  ditches,  we  are  told,  for  the  pur- 
pose of  thoroughly  draining  the  soil  under  the  road,  so  that  the 
frost  will  not  heave  or  destroy  the  road  surface,  a  theory  that  the 
writer  has  not  found  to  be  sustained  by  experience.  Even  granting 
that  a  shallower  ditch  would  leave  more  moisture  under  the  road 
that  would  freeze,  it  becomes  a  very  important  question  as  to  the 
effect  of  such  freezing,  and  the  writer  has  never  seen  any  deleter- 


Mocadam 


FIG.    1.  —  STANDARD   CROSS-SECTION   FOR    MACADAM    ROADS,    MAS- 
SACHUSETTS  HIGHWAY   COMMISSION. 

ious  results  in  ordinary  soil  where  the  road  bed  had  been  drained 
by  a  ditch,  whose  bottom  was  18  ins.  below  the  crown  of  the  road. 
As  to  theory,  it  seems  probable  that  any  expansion  of  the  moisture 
in  the  voids  of  the  earth  upon  freezing  would  be  taken  up  by  the 
12-in.  layer  of  dry  earth  between  the  frost  and  the  macadam  ;  and 
should  it  not  be  thus  taken  up,  it  would  merely  raise  the  whole 
surface  of  the  road  uniformly  a  fraction  of  an  inch.  It  may  be 
argued  that  "faulting"  may  be  caused  by  the  lateral  pressure  of 
frozen  earth  ;  if  so,  the  line  of  weakness  is  in  the  ditch  where  the 
bulging  will  occur  and  not  under  the  macadam  ;  and  it  is  erroneous 
to  assume  that  expansion  will  take  place  along  the  axis  of  the 


H 

FIG.    2.  —  CROSS-SECTION    OF    ROAD    WITH    GENTLE    CURVES    AND 
SHALLOW    DITCHES. 

road,  for  ice  melts  under  pressure  and  flows  toward  the  point  of 
least  resistance. 

Since  the  writer  formulated  this  theory  to  account  for  the  fact 
that  freezing  does  not  injure  macadam,  even  where  shallow  ditches 
are  used,  he  has  received  conclusive  proof  of  its  truth. 

Prof.  Daniel  B.  Luten's  recent  experiments  upon  the  expansion 
of  gravel,  sand,  and  loam,  saturated  with  water,  and  frozen  in  an 
iron  tube,  36  ins.  long,  filled  to  within  3  ins.  of  the  top,  showed  an 
expansion  of  %  in-  with  gravel,  %  in.  with  loam,  and  an  imper- 


*The  half-tone  illustrations  presented  further  on,  with  explanations 
and  comments  beneath  the  titles,  illustrate  the  two  types  of  cross-section, 
as  shown  by  completed  macadam  roads. 


CROSS-SECTIONS  5 

9 '  ' 

ceptible  amount  with  sand.  The  rest  of  the  expansion  was  taken 
up  by  forcing  water  up  through  the  earth,  and  forming  a  plug  of 
ice  at  the  top  of  the  tube ;  a  1-in.  ice  plug  on  the  gravel,  a  y^-in. 
plug  on  the  loam,  and  a  i^-in.  plug  on  the  sand. 

Under  a  road,  when  freezing  begins,  the  expansion,  in  a  similar 
manner,  will  force  a  small  amount  of  water  up  into  the  voids  of 
the  dry  layer  beneath  the  macadam,  out  into  the  ditches,  and 
down  into  the  earth  below,  thus  causing  no  perceptible  heaving  of 
the  macadam.  It  must  be  remembered  that  a  soil  is  seldom  sat- 
urated with  water  as  in  these  experiments  and  therefore  little  or 
no  expansion  of  the  soil  itself  will  take  place  under  ordinary  con- 
ditions. Since  it  is  evident  that  the  deep  ditches  are  usually  un- 
necessary, it  follows  that  broad,  shallow  ditches  are  better,  not 
only  because  less  earth  need  be  moved  to  form  them,  but  because 
by  giving  the  ditch  a  broad  (24-in.)  bottom,  drag  scrapers  can  be 
used  in  moving  the  earth.  This  leads  to  another  criticism  of  the 
common  design  of  road  cross-section  as  made  by  engineers  who 
seem  not  to  have  considered  the  great  economy  attending  the  use 
of  drag  and  wheel  scrapers  and  road  machines.  Deep,  narrow- 
bottomed  ditches,  and  the  "shoulders"  upon  each  side  of  the  ma- 
cadam, shown  in  Fig.  1,  render  the  use  of  such  machines  generally 
impracticable.  The  wheel  scraper  is  the  greatest  labor-saving 
device  for  moving  earth  short  distances  that  was  ever  invented, 
and  road  machines  and  leveling  scrapers  stand  second  only  in 
point  of  merit.  It  can  be  safely  said  that  where  these  machines 
can  be  used  the  cost  of  earthwork  will  be  not  over  two-thirds  what 
it  is  where  pick  and  shovel  work  is  necessary.  Wide,  shallow 
ditches  are  favorable  to  the  use  of  drag  and  wheel  scrapers  and 
all  that  remains  to  render  the  use  of  leveling  machines  possible  is 
a  gentle  curving  cross-section  profile  of  the  finished  earth  surface, 
as  shown  in  Fig.  2. 

The  cross-section  of  the  ditch  shown  in  Fig.  2  will  give  sufficient 
earth  to  build  the  embankment  forming  the  earth  road.  Here 
again  the  engineer  is  very  likely  to  err,  particularly  if  his  training 
has  been  in  railroad  work.  He  will  balance  his  cuts  and  fills  on 
the  longitudinal  profile  of  the  road,  and  entirely  forget  the  large 
amount  of  earth  that  will  come  from  the  ditches.  It  is  therefore 
a  good  rule  to  balance  in  the  usual  way  the  cuts  and  fills  on  the 
profile  of  the  center,  and  afterward  raise  the  grade  about  3  to  6 
ins.  all  along  the  road,  to  make  room  for  the  earth  from  the 
ditches.  While  Fig.  2  may  be  taken  as  a  standard  cross- section,  it 
should  be  modified  to  suit  local  conditions.  In  very  wet,  soggy 


6  EARTH    ROADS 

soil,  or  where  the  drainage  area  of  the  ditches  is  great,  the  ditches 
must  of  course  be  made  larger;  while  in  very  sandy  soil  little 
ditching  is  required,  for  a  certain  amount  of  moisture  in  sand  is 
desirable  to  hold  it  together. 

LONGITUDINAL  PROFILE.— Another  common  error  made 
by  railroad  and  canal  engineers  is  to  design  level  or  nearly  level 
grades  for  long  stretches  of  the  road.  In  road  work,  however,  the 
minimum  grade  should  be  y%%  to  secure  longitudinal  drainage  of 


FIG.    3. — MACADAM    ROAD    WITH    DEEP    DITCHES 

(Showing  a  New  York  State  macadam  road  of  "standard  cross-section" 
with  ditches  of  extreme  narrowness  at  the  bottom  and  of  unnecessary 
depth.  Owing  to  not  balancing  cuts  and  fills,  material  has  been  wasted  out- 
side of  ditch  line  and  in  front  of  fence  lines.) 

any  incipient  ruts  that  may  form  in  the  road  surface ;  and  this  is 
especially  necessary  in  cuts  where  the  water  seeps  through  and 
runs  down  the  slopes  of  the  cut,  frequently  washing  ditches  full 
of  earth  where  they  have  only  a  slight  grade.  This  leads  us  to  the 
consideration  of  cuts. 

Deep  cuts  form  the  most  expensive  portions  of  a  road,  both  in 
first  cost  and  maintenance.  To  reduce  the  first  cost  of  earthwork 
in  cuts,  the  surface  ditches  should  be  narrowed  until  they  are 
merely  gutters. 

GUTTERS  AND  DRAINS.— Gutters  must  be  paved  with  cob- 
blestone on  grades  of  2%  or  more.  Underneath  the  gutter,  tile 
drains  must  be  placed  to  carry  the  water  fed  by  the  ditches  above 


GUTTERS  AND  EMBANKMENTS  ? 

9 
the  cut.    It  should  be  observed  that  after  every  heavy  fall  of  snow 

the  mouths  of  all  such  drains  and  all  pipe  culverts  must  be  cleaned 
out,  otherwise  water  will  dam  back  and  under  pressure  will  either 
overflow  the  road  or  follow  along  the  pipe  and  undermine  it, 
causing-  bad  settlements. 

Regarding  the  width  of  the  road,  it  should  never  be  less  than 
15  ft.  between  ditches,  and  preferably  22  ft.  or  more.  The  surface 
should  not  have  a  side  slope  greater  than  %-in.  in  12  ins.,  other- 


FIG.    4.— MACADAM    ROAD    WITH    SHALLOW    DITCHES. 
(Showing-  macadam  (6  ins.  x  16  ft.)  road  without  ditches;  earth  shoulders 
7  ft.  wide;  crown  of  road  15  ins.  above  bottom  of  earth  gutter.) 

wise  traffic  will  follow  the  ridge  in  the  center,  and  more  quickly 
wear  it  out. 

EMBANKMENTS.— We  come  now  to  the  formation  of  em- 
bankments. The  scissors  and  paste-pot  engineers  usually  specify 
that  all  material  of  vegetable  nature  must  be  carefully  excluded 
from  the  embankments.  This  is  unnecessary  and  adds  immensely 
to  the  cost  where  the  road  passes  through  meadow  land.  It  is  of 
course  desirable  to  remove  brush,  large  roots,  and  high  weeds ;  but 
the  writer  has  built  embankments  in  the  densely  timbered  and 
brushy  country  of  western  Washington,  where  no  efforts  were 
made  to  exclude  small  twigs  and  sod,  and  after  eight  years  em- 
bankments showed  no  undesirable  settlement.  An  embankment 


8  EARTH    ROADS 

built  with  wheel  or  drag  scrapers,  wagons  and  horses,  needs  no 
rolling  until  its  surface  is  shaped  and  ready  for  completion; indeed 
the  "sectional  iron  roller,"  often  specified,  will  produce  no 
greater  consolidation  than  will  the  wheels  and  hoofs.  An  embank- 
ment need  not  be  made  in  horizontal  or  concave  layers,  as  fre- 
quently required  by  the  engineer.  All  such  "sandpapering"  is 
the  work  of  a  theorist,  which  experience  proves  unnecessary. 

In  passing,  the  writer  will  call  attention  to  a  common  error, 
namely,  that  embankments  shrink  some  10$  after  construction. 

Embankments  made  with  pick  and  shovel  and  wheelbarrows  do 
settle  under  the  puddling  action  of  rain,  but  in  embankments 
made  by  teams  the  shrinkage  takes  place  almost  entirely  during 
the  construction,  under  the  pounding  of  hoofs  and  wheels;  and 
even  very  high  embankments  so  constructed  do  not  ordinarily 
settle  over  2%  afterwards.  The  error  has  probably  arisen  from 
consideration  of  investigations  of  Morris  and  others,  showing  a 
shrinkage  of  10%  when  earth  is  taken  from  "cut"  and  put  into 
"fill."  It  is  true  that  shrinkage  takes  place,  but  the  shrinkage 
occurs  during  the  process  of  construction,  not  afterward.* 

COST  OF  EARTHWORK.— The  data  of  Morris,  as  copied  and 
erroneously  modified  by  Trautwine,  are  so  commonly  quoted  as 
being  exact  enough  for  practical  purposes,  that  the  writer  wishes 
here  to  state  that  not  one  of  Trautwine 's  tables  of  costs  comes 
within  25%  to  50%  of  the  truth  for  short  hauls,  either  with  carts, 
scrapers,  or  wheelbarrows.  Trautwine  unfortunately  underesti- 
mates the  cost  of  all  earthwork  except  for  long  hauls ;  and  there 
his  tables  are  useless,  since  two-horse  wagons,  which  he  does  not 
mention,  are  cheaper  than  carts.  The  writer  has  published  three 
handbooks!  for  engineers  and  contractors,  giving  all  his  data  and 
conclusions  in  full ;  but  for  the  present  'purpose  it  will  suffice  first 
to  point  out  some  of  the  causes  of  Trautwine 's  errors;  and  second 
to  give  the  writer's  own  rules  for  estimating  costs. 

Trautwine  errs,  (1)  in  assuming  that  a  wheel  scraper  or  drag 
scraper  holds  the  amount  of  earth  that  its  catalogue  size  would 
indicate,  because  it  will  usually  not  go  out  full ;  and  even  if  it 
does  it  is  full  of  loose-ploughed  earth  that  will  shrink  25%  when 
rolled  and  packed  by  hoofs  and  wheels;  he  errs  (2)  in  too  low  esti- 
mates of  time  lost  each  trip  in  loading  and  unloading;  he  errs  (3) 
in  the  speed  of  horses  going  at  a  walk ;  they  travel  not  150  ft.  a 
minute  as  stated  by  him,  but  220  ft.,  which  in  a  measure  counter- 


*See  Engineering-  News,  Nov.  15  and  22,  Dec.  13  and  20,  1900. 
fEarthwork   and   Its   Cost,    $2.00;    Rock   Excavation,    $3.00;    Handbook   of 
Cost   Data,   $4.00. 


COST  OP  EARTHWORK  9 

0      ' 

balances  some  of  his  other  errors  in  short  hauls ;  he  errs  (4)  in 
assuming  that  one  driver  can  look  after  three  or  more  carts.  In 
Trautwine's  table  of  costs  of  moving  earth  with  drag  scrapers  it 
is  stated  that  with  leads  of  40  ft.  one  drag  scraper  will  move  220 
cu.  yds.  in  10  hours,  which  is  absolutely  impossible.  The  writer 
has  never  seen  more  than  70  cu.  yds.  moved  with  one  scraper  in  a 
day  and  then  only  in  the  easiest  of  soil  and  with  shortest  of  hauls. 
It  is  high  time  that  engineers  should  cease  quoting  such  erroneous 
tables  of  costs — tables  that  have  caused  many  contractors  great 
financial  loss. 

The  following  are  the  writer's  rules  for  ascertaining  cost  of 
moving  earth,  not  including  superintendence  or  contractor's 
profits,  wages  of  laborers  being  15  cts.  per  hour,  of  team  and 
driver,  35  cts.  per  hour : 

The  length  of  lead  is  measured  in  feet  from  the  center  of  grav- 
ity of  the  cut  to  the  center  of  gravity  of  the  embankment,  no 
allowance  being  made  for  turning  around  at  either  end,  as  this 
is  included  in  the  "fixed  cost." 

The  fixed  cost  includes  cost  of  loosening,  loading,  dumping, 
spreading  and  lost  time  of  men  and  teams,  but  does  not  include 
superintendence  or  contractor's  profits  and  use  of  tools,  for  which 
at  least  25%  should  be  added.  It  is  absurd  to  talk  of  10%  or  15% 
profit  in  earthwork,  especially  in  a  new  and  unknown  soil. 

A  team  can  travel  at  a  walk  25  miles  in  10  hours,  or  at  a  speed 
of  220  ft.  a  minute.  A  laborer  will  load  with  a  shovel  about  15  cu. 
yds.  (place  measurement)  of  ploughed  earth  in  10  hours. 

A  plough,  team  and  driver  with  one  man  holding  the  plough, 
will  loosen  400  cu.  yds.  of  ordinary  earth  in  a  day ;  but  if  the  hard 
earth  crust  of  an  old  road  must  be  loosened,  it  will  take  two  teams, 
one  man  riding  the  beam  and  one  plough  holder,  to  loosen  about 
150  cu.  yds.  a  day. 

The  fixed  cost  of  moving  ordinary  earth  with  wagons  is  there- 
fore as  follows : 

Cts.  per 
cu.  yd. 

Ploughing   • 1 

Loading  wagon 10 

Spreading   . .  ,     2 

Time  lost  waiting  to  load  and  unload 5 

Total  fixed  cost  of  earth  in  wagon.  .  18 


Ill 


EARTH    ROADS 


To  this  18  cts.  add  4  to  6  cts.  if  very  tough  clay  or  old.  com- 
pacted crust  must  be  ploughed.  The  cost  of  hauling  is  as  follows: 
In  soft,  loose  soils  where  wagons  must  be  pulled  up  steep  (10'/$  ) 
embankments,  2-3  cu.  yd.,  place  measure,  is  an  average  load,  while 
over  fair  earth  roads  with  steep  pull  1  cu.  yd.  forms  a  load;  on 
hard,  level  earth  roads,  l1/^  cu.  yds.  is  a  load. 

Rule — To  the  fixed  cost  of  18  to  22  cts.  per  cu.  yd.  in  the  wagon 


FIG.   5.— DEEP  DITCH  AND  CULVERT   PARTIALLY   FILLED   WITH   DIRT 

WASHINGS 

(Showing-  12-in.  culvert  on  New  York  State  road  after  nature  has  begun 
to  obliterate  unsightly  ditches.  If  it  is  argued  that  so  large  a  ditch  is  neces- 
sary to  carry  the  surface  water,  why  are  culverts  made  of  less  than  one- 
eighth  the  carrying  capacity  of  the  ditch?) 

add  0.8  cts.  per  100  ft.  of  lead  in  soft  roads,  0.55  cts.  per  cu.  yd. 
per  100  ft.  over  fair  roads,  and  0.4  cts.  per  cu.  yd.  per  100  ft.  over 
good  earth  roads. 

Drag  scrapers  hold  on  an  average  only  0.1  cu.  yd.  and  the  fixed 
cost  is  about  10  cts.  per  cu.  yd.  of  ordinary  earth  for  leads  of  100 
ft.  or  less,  to  which  add  6  cts.  per  cu.  yd.  per  100  ft.  additional 
lead. 

No.  1  wheel  scrapers  average  0.2  cu.  yd.  per  load  and  the  fixed 
cost  of  earth  in  the  wheeler  is  10  cts.  per  cu.  yd.  for  100  ft.  lead  or 
less,  to  which  add  3  cts.  per  cu.  yd.  for  each  additional  100  ft.  lead. 

No.  2  wheel  scrapers  average  0.25  cu.  yd.  per  load,  so  that  the 


SURFACING 


11 


cost  of  hauling  is  21/1>  cts.  per  100  ft. ;  but  where  a  snatch  team  is 
necessary  in  loading,  3  cts.  per  cu.  yd.  is  added  to  the  fixed  cost. 

To  these  figures  for  cost  by  scrapers  or  wheelers  add  5  cts.  if 
tough  clay  or  hard  road  crust  must  be  excavated. 

A  study  of  the  above  will  disclose  the  fact  that  for  short  hauls 
no  method  compares  in  economy  with  the  drag  and  wheel  scrap- 


FIG.    6. — MACADAM  ROAD  ON   STEEP  GRADE,   WITH   SHALLOW- 
PAVED     GUTTERS. 

(Showing  macadam  (6  ins.  x  12  ft.)  road  with  broken  stone  gutters  (4 
ins.  x  5  ft.)  on  5.3  per  cent,  grade  up  which  a  team  hauls  a  gross  load  of 
12,000  lt>s.,  exerting  a  tractive  force  of  not  less  than  800  Ibs.) 

ers ;  indeed,  earth  can  be  moved  for  about  two-thirds  what  it  will 
cost  by  wagons,  up  to  200  ft.  lead. 

SURFACING.— The  surface  of  the  sub-grade  should  be  leveled 
either  with  a  Shuart  grader  or  one  of  the  common  road  machines. 
In  cuts  the  ploughing  should  extend  below  the  sub-grade  to  loosen 
up  the  earth  so  that  the  blade  of  the  machine  will  more  easily  fill 
up  the  depressions.  A  grader  will  readily  level  25,000  sq.  yds.  in 
a  day  at  a  cost  of  0.02  cts.  per  sq.  yd.  If  the  earth  road  thus  pre- 
pared is  to  be  macadamized,  it  should  be  thoroughly  rolled  with  a 
steam  roller  so  that  no  stone  will  be  afterward  pushed  down  into 
the  earth.  The  contractor  cannot  be  too  painstaking  in  this 
respect,  for  his  pocket-book's  sake,  if  he  is  to  be  paid  for  the  stone 
by  the  cubic  yard  in  place. 


12  EARTH    ROADS 

In  loose  sand  the  roller  cannot  be  used  at  all  without  first  cover- 
ing the  sand  with  a  layer  of  clay  or  loam,  or  thoroughly  soaking 
the  sand  with  water,  the  latter  practice  often  being  very  expens- 
ive. An  inch  of  fine  dust  spread  over  the  sand  and  washed  in  to 
fill  the  voids  will  be  found  effective  and  usually  less  expensive 
than  the  use  of  cotton  cheese-cloth  recommended  by  Massachusetts 
engineers.  Half -inch  to  l^-in.  screenings  from  the  crusher  may 
also  be  used  to  advantage;  for  by  spreading  a  layer  one  stone 
thick  and  rolling  it,  no  more  stone  will  be  lost  in  the  sub-grade.  A 
thin  coating  of  straw  has  also  been  used  to  hold  up  the  macadam 
on  a  sandy  soil,  and  other  expedients  will  suggest  themselves  to 
the  engineer  not  hide-bound  by  precedent. 

We  have  thus  far  considered  the  itemized  cost  of  moving  earth 
and  forming  the  surface.  The  following  two  examples,  taken  from 
the  writer's  timebooks,  show  the  total  cost  of  grading  a  mile  of 
road  under  varying  conditions.  The  first  case  shows  cost  of  work 
done  with  that  of  Fig.  2,  designed  by  the  writer. 

Case  I. — Cost  of  grading  and  surfacing  one  mile  of  road  in  or- 
dinary earth,  gravel  and  clay: 

90  days,  team  and  driver  on  scrapers,  at.  .  .   $3.50     $315 

60  days,  labor  on  scrapers 1.50         90 

10  days,  foreman 2.50         25 


Total,  3,000  cu.  yds.  excavated  at  14  1-3  cts.  $430 

In  Case  I.  all  hauls  were  short,  none  being  over  500  ft.,  and  the 
average  not  over  200  ft.;  no  "sandpapering"  of  slopes  was  re- 
quired, but  a  good,  substantial,  workmanlike  job  throughout. 

Case  II. — In  this  case  deep  ditches  were  dug  and  carefully 
trimmed,  the  cross-section  being  like  Fig.  I.  As  the  time-sheet 
shows,  there  was  very  little  teaming,  but  nearly  all  hand-work. 
Cost  of  grading  and  surfacing  one  mile : 

60  days,   team   and  driver,   on  plough   and 

wagon,  at $3.50     $210 

460  days'  labor .   1.50       690 

40  clavs,  foreman.  .  .   2.50       100 


Total,  4,500  cu.  yds.  excavated  at  22  1-5  cts.        #1,000 

There  was  less  hauling  in  Case  II.  than  in  Case  I.,  but  most  of 
the  earth  was  either  wasted  on  the  sides  of  the  ditches  or  thrown 
directly  into  the  road,  and  careful  trimming  was  required,  while 


TRACTION  •  13 

the  shoulders  and  general  form  of  the  cross-section  made  it  impos- 
sible to  use  graders. 

These  two  cases  strikingly  and  accurately  illustrate  the  differ- 
ence between  good  and  bad  engineering  design.  In  Case  I.,  using 
wheel  scrapers,  a  good  road  was  built  with  30%  less  excavation 
and  at  35%  less  cost  per  cubic  yard  than  in  Case  II.,  proving  the 
writer's  contention  that  road  design,  so  far  as  earthwork  is  con- 
cerned, may  be  greatly  improved  both  in  Massachusetts  and  New 
York  State. 

The  cost  of  earthwork  and  of  earth  roads  has  been  discussed, 
not  to  advocate  a  road  surfaced  with  earth,  but  because  an  earth 
road  must  be  made  upon  which  to  build  the  macadam  or  Telford 
pavement.  An  unpaved  earth  road  will,  it  is  true,  remain  in  good 
condition  when  travelled  by  wide-tired  wagons  until  the  fall  rains 
begin  to  soak  its  surface,  when  nothing  can  prevent  rutting  first, 
and  disintegration  by  frost  afterward. 

It  is  frequently  stated  that  an  earth  road  is  as  good  as  any  other 
kind  of  road  if  kept  well  drained  and  free  from  ruts,  which  re- 
minds the  writer  of  an  old  saying  that  a  certain  bronze  eagle  in 
Salt  Lake  City  "flies  down  to  get  a  drink  every  time  it  hears  the 
town  clock  strike."  The  statements  are  true  in  both  cases,  but 
the  conditions  are  equally  impossible  of  fulfillment. 

It  is  not  a  fact  that  an  earth  road  is  as  good  as  any  other  type, 
even  if  kept  free  from  ruts,  as  the  accompanying  table  of  the 
number  of  pounds  tractive  force  necessary  to  pull  a  ton  over  dif- 
ferent surfaces  clearly  shows : 

Lbs. 

Street  car  tramway 20 

Asphalt    25 

Stone  or  wood  block  pavement  (good) 30 

Macadam  or  plank  road   (good) 35 

Macadam  or  plank  road   (poor) 50 

Gravel,  good  hard  road 75 

Clay,  good  hard  road 100 

Earth,  loose 300 

It  is  evident  that  even  with  the  best  earth  road  only  half  as 
great  a  load  can  be  hauled  as  on  a  good  macadam  road,  which  is 
in  itself  sufficient  to  condemn  an  earth  road  for  any  but  a  poverty- 
stricken  community. 

TRACTION  AND  TRACTIVE  POWER.— This  leads  naturally 
to  a  brief  consideration  of  traction  and  tractive  power.  All  au- 


14  EARTH    ROADS 

thorities  agree  that  a  horse  cannot  exert  a  continuous  pull  of  more 
than  100  to  150  Ibs.  for  eight  to  ten  hours,  going  at  a  speed  of  2l/2 
miles  an  hour,  and  authorities  state  that  for  a  short  period  of  time 
a  horse  may  exert  double  his  average  tractive  force,  or  about 
250  Ibs. 

The  writer  has  found  that  a  horse  may  exert  500  Ibs.  tractive 
force  without  injury  for  at  least  two  hours  out  of  ten.  He  has 
used  a  team  for  raising  a  2,000-lb.  pile  hammer,  where  the  power 
was  multiplied  three  times  by  pulleys,  and  the  team  has  worked 
about  three  hours  a  day,  actually  lifting  a  weight  equivalent  to 
about  666  Ibs.  dead  lift,  which,  with  friction,  was  not  less  than 
1,000  Ibs.  tractive  force  exerted  by  the  team.  Tests  made  by  the 
U.  S.  Agricultural  Department  showed  that  a  pair  of  small  mules 
exerted  a  continuous  pull  on  a  trachometer  of  1,000  Ibs.  while 
hauling  a  wagon  up  a  steep  hill.  (See  Fig.  6  for  a  view  of  finished 
macadam  road  with  5.3%  grade.) 

It  may  be  safely  said,  therefore,  that  a  team  can  exert  four 
times  as  much  tractive  energy  going  up  a  short  hill  as  its  average 
pull  upon  the  level.  Each  added  l(/f  of  grade  is  equivalent  to  an 
added  resistance  to  traction  of  about  20  Ibs.  per  ton;  therefore, 
if  the  average  load  of  a  wagon  is  8,500  Ibs.,  and  the  weight  of  the 
wagon  is  1,500  Ibs.,  the  tractive  force  necessary  to  pull  it  over  a 
good  macadam  road  on  the  level  would  be  175  Ibs.,  or,  over  a  poor 
macadam  road,  250  Ibs.,  which  would  still  leave  about  750  rbs. 
available  tractive  force  that  a  team  could  exert  going  up  a  short 
hill,  such  a  hill  having  a  grade  of  71/i></^  •  It  is  probable  that  on  a 
smooth  macadam  road,  and  on  a  grade  as  steep  as  T1/^,  the 
horses  might  slip  and  fall,  so  that  some  allowance  should  be  made 
for  this  contingency. 

It  is  seldom,  however,  that  any  such  loads  as  this  are  hauled 
even  over  good  roads,  simply  for  the  reason  that  there  are  usually 
stretches  of  poor  road  to  be  travelled  by  the  farmer  before  the 
good  road  is  reached ;  and  for  many  years  to  come,  certainly  not 
within  the  life  of  macadam  pavements  built  in  the  next  few  years, 
the  average  net  load  will  probably  not  exceed  three  tons,  which 
would  enable  a  team  to  climb  a  short  8%  grade  without  overtax- 
ing its  energies.  Since  it  is  generally  a  few  short  deep  cuts  that 
add  so  greatly  to  the  cost  of  a  road  it  would  seem  to  be  good  en- 
gineering not  to  endeavor  to  reduce  the  grades  where  much  earth- 
work is  necessary,  without  careful  consideration  of  the  above 
stated  facts.  A  2%  or  3^  grade  forms  a  desirable  maximum  if  it 
can  be  cheaply  obtained,  since  2%  or  3%  is  the  slope  of  repose  of 


LOCATION  f  15 

a  wagon  on  a  macadam  surface,  and  a  horse  can  in  consequence 
readily  trot  down  such  a  grade. 

Having  considered  the  design  of  cross-section,  the  cost  of  exca- 
vation and  surfacing,  and  the  selection  of  maximum  grades  or  de- 
sign of  profile,  let  us  now  briefly  consider  the  subject  of  the  gen- 
eral location  of  the  road. 

LOCATION. — Upon  this  subject  alone  a  volume  could  be  writ- 
ten, but  much  already  exists  in  print  and  it  is  not  the  purpose  of 
the  writer  to  "re-hash,"  but  rather  to  call  attention  to  facts  which 
hitherto  have  not  received  publication,  or,  if  published,  have  not 
become  generally  known.. 

Few  existing  roads  are  well  located.  They  are  built  after  the 
style  of  the  Romans,  going  over  hills  rather  than  around  them. 
Any  civil  engineer  would  remedy  such  a  glaring  defect  if  given 
the  opportunity ;  but  there  is  one  point  in  location  that  the  engin- 
eer is  almost  certain  to  overlook  if  his  experience  has  been  in  rail- 
road work,  namely,  the  character  of  the  soil  over  which  the  road 
runs.  Upon  one  side  of  a  valley  the  surface  may  be  clay,  upon  the 
opposite  side  gravel ;  in  the  bottom  of  the  valley  the  soil  is  usually 
alluvial,  higher  up  on  a  bench  it  is  generally  far  more  fit  for  road 
purposes.  The  experienced  engineer  will  therefore  not  select  the 
final  location  of  a  road  until  he  has  studied  sub-surface  conditions 
as  well  as  topography.  In  locating  a  road  in  a  new  country  the 
engineer  will  also  bear  in  mind  the  fact  that  one  of  the  greatest 
items  of  cost  of  a  gravel  or  macadam  road  is  the  hauling  of  ma- 
terial, and  will  locate  his  road  near  the  gravel  pits  or  proposed 
quarry,  wherever  possible.  A  few  culverts  or  drains  or  a  few 
bridges  will  greatly  swell  the  cost  per  mile  of  road,  and  these  like- 
wise the  engineer  will  avoid  if  possible ;  and  where  necessary  will 
build  them  as  cheaply  as  may  be,  using  vitrified  pipe  or  timber  for 
small  culverts,  instead  of  masonry  arches  or  iron  pipe ;  using  steel 
I-beams  with  wooden  floors  for  bridges  under  30  ft.  span,  instead 
of  the  expensive  Pony  trusses  so  common  in  the  eastern  states.  It 
is  not  unusual  to  see  highway  bridges  of  60  ft.  or  more  span  over 
streams  that  never  carry  much  driftwood  or  ice  (the  greatest  de- 
stroyers of  piers),  where  two  or  more  30-ft.  spans  resting  on  pile 
foundations  would  suffice,  at  far  less  expense.  Bridges  may  fre- 
quently be  avoided  entirely  by  diverting  the  stream,  which  is  a 
common  and  economic  expedient  in  the  far  west. 

To  sum  up  this  chapter,  we  find:  (1)  A  uniform  cross-section 
for  all  parts  of  the  road  should  not  be  adopted.  The  depth  of 
ditches  should  be  made  to  vary  with  the  character  of  the  soil,  very 


16  GRAVEL  ROADS 

shallow  in  sand  or  on  steep  grades,  and  deep  in  flat,  soggy  lands, 
but  ordinarily  not  much  more  than  a  foot  below  the  general 
ground  level.  The  ditches  should  be  wide  enough  to  permit  the 
use  of  drag  and  wheel  scrapers,  and  engineers  should  cease  blindly 
copying  plans  made  long  before  the  invention  of  the  wheel  scraper 
and  other  labor-saving  devices. 

(2)  Freezing  of  the  soil  does  not  destroy  a  macadam  or  other 
road   crust,   provided   there   is   1    ft.    of  dry   earth   beneath   the 
macadam. 

(3)  The  cuts  and  fills  should  be  balanced,  including  the  earth 
from  the  ditches.     No  sandpapering  of  slopes  and  embankments 
should  be  specified. 

(4)  Select  a  profile  with  a  minimum  grade  of  y>(/f:  and  a  maxi- 
mum grade  of  3%,  if  it  can  be  obtained  at  nominal  cost ;  but  up  to 
5%,  or  even  8%,  if  necessary  to  avoid  expensive  excavation,  for 
the  tractive  power  of  a  horse  is  not  a  constant  quantity  and  is 
greater  than  authorities  state. 

(5)  Design  a  rather  flat  arch  for  the  road  surface,  with  a  total 
crown  or  drop  of  ViH11-  in  12  ins.,  and  avoid  any  shoulders  or 
trenches  in  the  cross-section.     Thus  will  it  be  possible  to  do  the 
surfacing  by  horse  instead  of  by  man  power. 

(6)  Locate  the  road  with  due  regard  to  the  character  of  under- 
lying soil,  shifting  it  where  possible  to  secure  better  material  both 
for  sub-grade  and  for  surfacing. 

(7)  Cut  down  the  cost  of  all  culverts  and  bridges  as  low  as  pos- 
sible, both  by  careful  location  of  the  road  and  by  economy  in  the 
design  of  culverts  and  bridges. 


Chapter  III. 
GRAVEL  ROADS. 

As  compared  with  earth  roads,  next  in  point  of  economy  in  first 
cost  are  gravel  roads.  As  usually  constructed  they  are  but  little 
better  than  earth  roads,  f or  the  simple  reason  that  any  gravel  is 
considered  good  enough,  and  no  care  is  taken  to  screen  out  the 
poor  material  from  the  good.  More  than  30%  of  sand  or  loam 
destroys  the  effectiveness  of  gravel,  rendering  it  pervious  to  water 
and  consequently  unserviceable.  It  may  be  set  down  as  an  almost 
infallible  rule  that  gravel  should  be  screened,  not  only  to  exclude 
an  excess  of  fines,  but  to  insure  an  even  distribution  of  fine  and 
coarse  material  when  placed  in  the  road.  Where  a  small  amount 


GRAVEL  ROADS  .  17 

of  gravel  is  required,  the  ordinary  inclined  stationary  screen, 
against  which  the  gravel  is  thrown  by  shovel,  will  suffice ;  but  for 
extensive  work  it  is  cheaper  to  use  a  stone-crushing  plant  with 
elevator,  rotary  screen  and  bins,  thus  breaking  the  very  large  peb- 
bles, while  by  storing  the  gravel  in  bins  the  expense  of  loading 
with  shovels  into  wagons  is  avoided,  and  the  team  loses  very  little 
time  in  waiting  to  be  loaded.  To  save  cost  in  handling,  the  un- 
screened gravel  should  be  shoveled  into  small  dump  cars,  hauled 
on  a  track  up  an  incline  and  dumped  directly  over  a  chute  feeding 
into  the  crusher.  With  eight  men  loading  cars,  one  horse  and 
driver  hauling,  one  bin  man  and  one  engineer,  the  output  should 
be  150  cu.  yds.  of  all  sizes  of  material  in  10  hours,  part  of  which 
will  probably  be  waste,  an  excess  of  fines  being  usually  obtained. 
With  labor  at  15  cts.  per  hour  the  cost  of  screening,  including 
coal  and  engineer,  but  not  rent  of  plant,  will  be  about  15  cts.  per 
cu.  yd. ;  since  probably  one-third  of  the  output  will  be  waste,  the 
cost  of  useful  product  will  ordinarily  be  about  20  cts.  per  cu.  yd. 
in  the  wagon.  The  cost  of  hauling  and  rolling  will  be  found  in 
the  following  chapter,  being  the  same  as  for  macadam.  The  screen 
should  have  three  sizes  of  circular  openings,  %  in.,  1%  and  2% 
ins.  in  diameter.  Considerable  variation  may  be  made  from  these 
sizes  if  experience  with  the  material  used  gives  better  results. 

Engineers,  and  especially  young  engineers,  are  prone  to  accept 
all  that  is  published  regarding  "the  proper  sizes"  and  other  de- 
tails of  construction  without  asking  the  reason  why.  The  writer 
cannot  too  strongly  urge  the  necessity  of  less  empiricism  and 
more  rationalism  on  the  part  of  both  authors  and  readers.  We  are 
all  too  apt  to  believe  that  the  particular  way  in  which  we  have 
overcome  some  difficulty  or  solved  some  problem  is  the  best  and 
only  right  way,  when  in  fact  there  probably  are  other  and  better 
methods.  Even  at  the  risk  of  being  accused  of  digression  the 
writer  wishes  to  emphasize  this  contention  by  an  example.  For 
years  it  has  been  customary  to  specify  that  no  stone  in  a  broken 
stone  road  shall  be  over  2Vi>  ins.  in  diameter,  because  it  is  claimed 
that  if  larger  it  will  work  to  the  surface.  There  is  no  doubt  that 
if  a  mass  of  loose  stone  of  various  sizes  is  passed  over  by  wheels 
the  larger  stones  will  tilt  up  when  the  weight  comes  upon  one  end 
of  them  and  the  smaller  stones  will  roll  down  into  the  place  made 
vacant  by  such  tilting,  and  by  a  repetition  of  this  process  the 
larger  stones  work  to  the  surface.  But  it  does  not  follow  that  in 
a  gravel  or  broken  stone  road,  rolled  with  a  steam-roller  and 
bound  together  with  the  addition  of  fines,  a  stone  will  work  to 


J8  GRAVEL  ROADS 

the  top  if  it  is  2  ins.  below  the  surface1  to  begin  with.  In  fact,  the 
mass  is  so  perfectly  bound  together  that  it  is  impossible  for  tilting 
to  take  place.  In  the  city  of  Rochester,  the  writer  has  seen  sec- 
tions of  old  macadam  pavements  where  stones  5  ins.  long  are  to 
be  found' scattered  indiscriminately  through  the  mass,  apparently 
just  as  they  had  been  placed  ten  years  before.  (Jreat  as  was 
Macadam,  careful  as  were  his  observations,  and  sound  as  are 
many  of  his  conclusions,  it  is  evident  that  in  this  case  his  rule 
that  "no  stone  larger  than  will  enter  a  man's  mouth  should  go 
into  a  road,"  does  not  apply;  for  we  use  a  binder  where  he  did 
not ;  we  use  a  steam-roller  where  he  did  not;  and  these  two  factors 
make  all  the  difference  in  the  world  in  the  behavior  of  the  stone 
forming  a  macadam  pavement.  Therefore,  let  us  not  be  dogmatic 
in  naming  limiting  sizes  of  stone  to  be  used  in  road  construction, 
especially  for  the  lower  courses. 

To  return  to  the  screening.  The  gravel  passing  through  a  l1/^- 
in.  screen  will  probably  contain  most  of  the  softer  varieties  <>l 
stone,  while  the  gravel  passing  through  the  21/»-in.  screen  will  be 
of  harder  consistency ;  the  smaller-sized  stone  should  therefore 
form  the  lower  layer  of  the  road,  and  the  larger,  tougher  sizes 
the  surface.  It  will  require  about  one  load  of  the  screenings  (less 
than  Vii-m-  in  diameter)  to  every  four  loads  of  the  larger  sizes  to 
fill  their  voids  and  bind  them  together;  and  the  screenings  should 
be  spread  over  the  larger  gravel,  sprinkled,  and  rolled  with  a 
steam-roller  until  perfectly  compact,  the  method  used  being  much 
the  same  as  described  for  macadam  in  the  next  chapter.  Fre- 
quently the  smaller  and  rounded  gravel  cannot  be  rolled  before 
the  addition  of  the  screenings,  as  it  will  push  before  the  roller  in 
a  wave ;  while  the  top  course  of  stone,  if  it  has  any  sharp-edged 
pieces,  due  to  the  crushing  of  larger  fragments,  may  be  rolled 
before  the  addition  of  screenings.  It  has  been  claimed  by  some 
engineers  that  the  rounded  form  of  the  fragments  of  a  broken 
cobble  or  large  pebble  make  gravel  unfit  for  road  purposes,  as  it 
tends  to  rock  under  a  load  and  so  breaks  the  bond,  rendering  the 
road  unstable.  The  writer  does  not  agree  with  this  theory,  be- 
cause even  a  poor  gravel  road  S!IOWTS  no  sign  of  instability  ki 
summer,  and,  furthermore,  a  stone  thoroughly  supported  .on  all 
sides  by  a  binder  of  sand  or  the  like  cannot  rock. 

The  real  cause  of  the  failure  of  most  gravel  roads  is  carelessness 
in  selection  of  materials,  and  utter  absence  of  judgment  in  con- 
struction, and  while  a  gravel  road  will  probably  have  to  be  thicker 
than  a  macadam  road  for  equal  supporting  power,  it  remains  a 


MACADAM    ROADS  *  19 

fact  that  good  gravel  roads  have  been  built  even  without  screen- 
ing out  the  excess  of  fines,  and  still  better  ones  can  be  built  by 
following  the  method  of  preparation  and  construction  outlined 
above.  The  writer  must  not  be  misunderstood  as  arguing  for 
gravel  in  place  of  macadam.  The  latter  is  always  to  be  preferred 
as  a  matter  of  ultimate  economy,  where  good  ledge  rock  is  obtain- 
able with  a  moderate  haul,  for,  as  will  be  shown  later,  the  cost  of 
quarrying  is  usually  not  to  exceed  50  cts.  per  cu.  yd.,  while  the 
cost  of  handling  and  screening  gravel  is  almost  as  great  as  the 
cost  of  crushing  stone,  leaving  the  other  items  of  cost  for  both 
macadam  and  gravel  practically  identical,  if  the  haul  is  the  same. 
This  would  make  a  difference  in  cost  of  about  25/£  only,  in  favor 
of  a  gravel  road  as  compared  with  macadam.  Should  good  stone 
for  macadam  surfacing  be  expensive,  and  no  suitable  quarry  stone 
be  available  even  for  the  lowe'r  course,  gravel  can  be  profitably 
used  in  place  of  the  stone  for  the  body  of  the  road,  which  may 
be  surfaced  with  3  ins.  of  imported  trap  or  other  suitable  rock. 
Telford  resorted  to  this  form  of  construction,  but  it  seems  not  to 
have  been  mentioned  in  modern  text-books. 


Chapter  IV. 
MACADAM  ROADS. 

The  non-professional  reader  may  have  wondered  why  a  mass  of 
broken  stone,  when  sprinkled  and  rolled,  finally  becomes  a  solid 
pavement,  impervious  to  water,  acting  in  all  respects  like  con- 
crete, although  110  cement  mortar  has  been  used.  That  such  a 
result  could  be  obtained  seems  not  to  have  occurred  to  any  one 
before  the  time  of  Tresaguet,  and  even  he  did  not  trust  to  the 
broken  stone  alone  to  sustain  loaded  wagons,  for  he  used  an  un- 
derpinning or  "bottoming"  of  large  paving  stone.  It  was  Ma,- 
cadam  who,  some  eighty  years  ago,  by  omitting  the  bottoming, 
showed  conclusively  that  broken  stone  possesses  the  property  of 
knitting  together,  or  becoming  cemented  under  the  rolling  action 
of  passing  Avheels.  The  writer  doubts  whether  Macadam  himself 
understood  the  philosophy  of  this  cementing  action,  and,  judged 
by  ^the  various  explanations  offered,  it  is  questionable  whether 
modern  engineers  have  fully  comprehended  the  real  cause. 

WHAT  HOLDS  MACADAM  ROADS  TOGETHER  ? 

There  are  those  who  say  that  the  roller,  by  shaking  and  pound- 
ing the  mass  of  loose,  broken  stones  placed  on  a  road,  finally  com- 


20  MACADAM  ROADS 

presses  the  stones  together  until  they  are  almost,  if  not  quite,  as 
compact  as  solid  rock.  This  they  tell  us  is  the  true  explanation 
of  the  binding  under  the  roller.  There  are  two  objections  to  their 
theory:  (1)  The  roller  does  not  compress  the  stone  to  its  original 
volume;  that  is,  it  does  not  reduce  the  voids  to  zero;  (2)  a  road 
is  never  bound  when  the  rolling  is  finished,  unless  a  binder  has 
been  added.  As  a  matter  of  fact,  rolling  does  not  reduce  the  voids 
of  the  mass  of  hard,  broken  limestone  more  than  one-half,  leaving 
at  least  20%  voids.  This  the  writer  has  determined  by  tests  over 
several  miles  of  road  where  the  output  of  the  crusher  was  care- 
fully measured  in  wagons,  and  afterward  measured  rolled  in 
place.  As  corroborative  evidence,  the  writer  refers  to  the  Trans- 
actions of  the  American  Society  of  Civil  Engineers,  for  1899, 
wherein  Mr.  W.  C.  Foster  states  that  in  one  instance  7.38  ins.  of 
loose  trap-rock  was  rolled  to  6  ins.,  while  Mr.  Cudworth  states 
that  in  another  instance  3.9  ins.  was  rolled  to  3  ins.  It  is  well 
known  that  the  voids  in  loose,  machine-broken  stone  are  about 
40%,  and  in  order  to  reduce  these  voids  to  zero,  6  ins.  would  have 
to  be  rolled  to  3.6  ins.  Upon  a  firm  foundation,  where  no  stone 
can  be  lost  in  the  sub-grade,  and  so  deceive  the  experimenter,  no 
one  has  ever  rolled  6  ins.  of  hard,  broken  stone  to  4  ins.,  or  re- 
duced the  voids  to  as  low  as  even  6%  ;  and,  common  as  is  the  false 
statement  in  text-books  (and  New  York  State  specifications)  that 
this  has  been  or  can  be  done,  the  statement  may  be  traced  to  one 
authority,  namely,  Macadam,  who  undoubtedly  did  see  6  ins. 
brought  down  to  4  ins.,  but  it  took  months  to  do  this  under  the 
wearing  action  of  hoofs  and  wheels,  which  was  not  rolling  but 
crushing  the  stone.  Were  any  further  evidence  necessary  to 
prove  this  contention  it  might  be  found  by  observing  the  volume 
of  screenings  or  binder  necessary  to  fill  the  voids  in  a  well-rolled 
macadam ;  and  the  amount  of  screenings  required  is  never  less 
than  20%  of  the  volume  of  the  rolled  metal,  where  no  screenings 
are  wasted  and  the  voids  are  completely  filled.  We  therefore  con- 
clude that  the  interlocking  of  the  fragments  of  stone  does  not 
account  for  the  binding.  What  then  does  cause  the  binding  of  a 
macadam  road?  Evidently  the  screenings  or  binding  materials 
are  essential.  Certain  authorities  tell  us  that  the  screenings  have 
a  cementing  property  akin  to  the  cementing  action  of  quicklime 
or  iron-rust.  In  other  words,  that  crystallization  or  setting. takes 
place.  Again  the  writer  cannot  agree  with  the  authorities.  A 
true  explanation  of  the  phenomenon  seems  to  be  found  in  a  study 
of  the  sand  on  a  sea  beach. 


BINDING  21 

• 

Where  the  waves  break,  the  sand  is  firm  and  makes  a  very  fair 
road  itself,  while  a  little  farther  back,  beyond  the  reach  of  the 
waves,  the  sand  is  loose  and  yielding.  The  waves  have  evidently 
been  the  means  of  binding  the  sand. 

Each  wave  as  it  rushes  up  on  to  the  beach  carries  in  suspension 
an  amount  of  fine  sand  that  is  precipitated  upon  the  surface  of  the 
beach  where  the  wave  breaks  and  is  washed  down  into  the  voids 
of  the  larger  particles  of  sand,  thus  puddling  or  filling  up  all  large 
interstices;  but  there  is  one  more  necessary  condition  to  secure 
firmness  and  sustaining  power,  the  sand  must  be  moist.  The  fine 
capillary  pores  hold  the  water,  or  rather  the  water  in  the  pores 
holds  the  sand  together  by  virtue  of  its  surface-tension,  a  well- 
known  physical  phenomenon;  and  it  is  this  surface-tension  or 
viscosity  of  water  that  binds  the  sand  together  and  makes  of  the 
sand  beach  an  excellent  surface  to  walk  or  drive  over.  Strange 
as  it  may  seem,  dust  and  water,  commonly  considered  the  two 
greatest  enemies  of  good  roads,  are,  when  in  their  proper  places, 
the  two  elements  that  prevent  the  disintegration  of  macadam.  The 
writer  conceives  that  the  authorities  have  been  wrong  in  their 
theories  and  that  macadam  is  first  bound,  not  by  a  cementing 
action,  but  by  the  surface-tension  of  water  in  the  capillary  voids 
of  the  screenings,  and  he  offers  the  following  facts  as  evidence  of 
the  truth  of  this  theory : 

(1)  A  road  built  without  screenings  will  not  bind  unless  it  is 
left  long  enough  under  the  action  of  hoofs  and  wheels  to  produce 
screenings. 

(2)  A  road  built  with  screenings  will  not  bind  if  all  the  dust  has 
been  taken  out  of  the  screenings,  leaving  only  the  coarser  par- 
ticles, but  will  bind  immediately  upon  the  addition  of  the  dust  and 
water.     The  writer  has  tried  this  experiment  under  the  direction 
of  a  "good  roads  expert"  who  had  ordered  all  the  dust  to  be 
screened  out,  under  the  mistaken  idea  that  it  would  be  injurious 
to  leave  it  in ;  but,  as  stated,  it  was  found  impossible  to  bind  the 
road  until  the  dust  was  spread  over  its  surface  and  washed  into 
the  voids. 

(3)  A  road  will  not  bind  until  sprinkled,  even  after  the  screen- 
ings or  binder  have  been  added. 

(4)  Time  for  iron-rust  or  other  cementing  action  to  take  place 
is  not  necessary.    A  newly  bound  road,  one  that  can  be  picked  to 
pieces  without  evidence  of  any  cementation,  will  uphold  a  heavy 
wagon,  behaving  exactly  like  an  old  road. 

(5)  The  screenings  of  a  very  hard  rock  like  trap  bind  slowly, 


22  MACADAM  ROADS 

sometimes  not  at  all,  due  to  insufficiency  of  dust  necessary  to  pro- 
duce capillary  voids;  but  upon  addition  of  a  little  sand  or  road- 
sweepings,  bind  immediately.  Conversely,  the  screenings  of  a  soft 
rock,  like  limestone,  rich  in  dust,  bind  quickly. 

(6)  Hygroscopic  rocks  (those  that  condense  moisture  upon  their 
surfaces),  like  limestone,  furnish  better  screenings  for  binding 
and  do  not  ravel  as  quickly  in  dry  weather  as  siliceous  or  quartz- 
like  rocks. 

(7)  Long-continued  drought  causes  macadam  to  ravel  and  final- 
ly go  all  to  pieces,  while  it  immediately  knits  together  again  after 
a  rain. 

(8)  Macadam  in  tunnels,  where  not  sprinkled,  soon  ravels,  as 
do  likewise  windswept  roads  that  are  kept  free  from  sufficient 
dust  and  moisture. 

The  writer  is  not  to  be  understood  as  advocating  the  use  of  dust 
and  water  alone  to  produce  binding,  rolling  being  quite  as  im- 
portant a  factor,  if  a  road  is  desired  that  will  retain  a  smooth  sur- 
face. Rolling  in  the  first  place  so  consolidates  the  stone  that  there 
is  little  chance  for  play  or  movement,  while  the  screenings  and 
water  added  render  appreciable  movement  impossible. 

Sand  and  water,  or  screenings  and  wrater,  though  not  a  true 
mortar,  serve  the  same  purpose,  as  we  have  seen,  and  the  less  mor- 
tar in  any  masonry  structure  the  more  perfect  and  durable  it  is. 

It  may  be  asked  wThat  connection  the  dust-water  theory  of  bind- 
ing above  outlined  has  to  do  with  economic  road  construction,  for 
good  roads  have  been  built  by  those  to  whom  such  a  theory  has 
never  occurred,  in  fact  by  those  to  whom  the  word  theory  means 
anything  entirely  barren  of  practical  results.  A  true  theory  is, 
however,  not  without  economic  value. 

Much  time  has  been  spent  and  much  money  wasted  in  vain  en- 
deavor to  bind  trap-rock  without  screenings  or  writh  screenings 
containing  insufficient  dust  to  make  capillary  voids.  All  this 
would  have  been  saved  had  the  true  theory  of  binding  been  under- 
stood. Indeed,  it  is  not  uncommon  to  see  it  stated  that  trap-rock 
screenings  are  totally  unfit  for  binding,  and  they  are  rejected  and 
Tompkins  Cove  limestone  screenings  or  the  like  substituted  at 
greater  cost.  The  writer  has  found  that,  if  upon  a  road  partially 
bound  with  trap  screenings,  a  little  limestone  dust  or  road  sweep- 
ings is  added,  the  binding  is  immediately  effected.  Thus  not  only 
is  unnecessary  rolling  in  vain  endeavor  to  bind  with  trap  s<?reen- 
ings  avoided,  but  the  screenings  are  made  available  at  probably 
less  cost  than  imported  limestone,  and  no  product  of  the  crusher 
is  wasted. 


QUALITY  OF  STONE  28 

Where  limestone  screenings  or  dust  is  not  £o  be  had,  a  little 
sand  sprinkled  over  the  road  and  washed  in  will  serve  the  pur- 
pose. Another  practical  application  of  the  theory  in  question  is 
the  following:  If  the  surface  material  is  brought  from  a  long 
distance  at  considerable  expense  for  freight  and  hauling,  it  will 
pay  not  to  import  the  screenings  also,  but  to  use  gravel  and  sand 
from  some  nearby  pit  for  a  binder. 

Many  trap-rock  macadam  streets  in  Rochester  have  been  bound 
with  gravel,  and  where  the  rolling  has  been  sufficient  the  surface 
remains  in  excellent  condition,  even  under  heavy  traffic. 

This  expedient  alone  results  in  a  saving  of  at  least  50  cts.  per 
cu.  yd.  of  macadam  in  the  matter  of  binding,  or  a  saving  of  $800 
per  mile  of  macadam  road  6  ins.  thick  and  16  ft.  wide.  It  will 
occur  to  the  practical  man  that  the  theory  is  not  without  economic 
value  if  by  its  application  so  large  a  sum  can  be  saved  per  mile  of 
road  construction. 

The  Massachusetts  Highway  Commission  is  conducting  a  series 
of  experiments  to  determine  the  cementing  value  of  the  dust  of 
different  rocks;  and  while  the  writer  is  not  prepared  to  dogmat- 
ically assert  that  these  experiments  will  prove  entirely  fruitless,  he 
thinks  it  probable  that  work  is  being  done  in  a  barren  field.  There 
may  be  some  true  cementing  action  in  the  crust  of  an  old  macadam 
road,  and,  if  so,  it  probably  aids  slightly  In  distributing  the  load 
upon  the  earth  foundation ;  but  it  certainly  has  no  effect  for  some 
time  after  a  road  is  built,  and,  once  the  cement  bond  is  broken  by 
the  blow  of  hoof  or  wheel,  it  cannot  re-form  immediately,  if  at  all. 
Cementation  of  any  value  is  therefore  secondary.  We  conclude, 
that  as  screenings  have  no  mysterious  cementing  function  to  per- 
form, they  are,  as  indicated  by  our  theory  and  borne  out  by  prac- 
tice, almost  equally  good  whatsoever  their  composition,  provided 
only  they  are  somewhat  hygroscopic,  but  not  clayey,  and  con- 
tain enough  fine  dust  to  form  capillary  voids. 


QUALITY  OF  STONE. 

Passing  now  to  the  actual  construction  of  a  macadam  road,  we 
have  first  to  consider  the  kind  of  stone  that  should  be  selected. 
We  find  in  point  of  durability  against  wear  that  the  order  fol- 
lowed in  the  accompanying  table  indicates  the  best  material,  the 
coefficients  of  wear  being  those  given  in  the  report  of  the  Massa- 
chusetts Highway  Commission  for  1899: 


24  MACADAM    ROADS 

RELATIVE  WEARING  POWERS  OF  DIFFERENT  STONE. 

Coefficient 
of  wear. 

Basalt    (trap) 18.5  to  30.5 

Diabase     "       11.4"   28.6 

Sandstone 10.5 "   19 

Quartzite    9.1  "   20.4 

Granite   8.4 "   17.9 

Syenite   12.6 

Schist 11.4"   12.2 

Limestone    6.3 "   17.2 

Gneiss 6.1  "   14.6 

Slate    8.5 

Mica  Schist 4.9 

Marble    2.9 

These  tests  were  made  in  a  rattler  and  are  therefore  not  entirely 
satisfactory,  serving  only  in  a  general  way  to  indicate  what  kind 
of  rock  is  ordinarily  the  most  durable  when  subject  to  attrition. 
The  table  also  shows  the  great  variability  of  specimens  of  the  same 
class  of  rock  coming  from  different  sections  of  the  country,  but  it 
is  evident  that  despite  these  variations  trap-rock  is  ordinarily 
twice  as  durable  as  hard  limestone,  and  four  times  as  durable  as 
soft  limestone.  It  will  therefore  pay  to  surface  a  macadam  road 
with  crushed  trap,  even  where  it  costs  twice  as  much  as  limestone. 
Marble  it  will  be  seen  is  practically  worthless.  Atmospheric  in- 
fluence has  a  great  effect  upon  the  durability  of  a  stone,  for  a  rock 
that  readily  absorbs  water,  as  does  a  loose-grained  sandstone  or 
slate,  will  quickly  go  to  pieces  under  the  action  of  frost ;  further- 
more, the  cementing  matrix  in  a  sandstone  is  frequently  quite 
soluble  in  the  acidulated  water  that  is  found  on  a  road  surface. 
Professor  Shaler  considers  limestone  to  be  twice  as  durable  as 
sandstone;  in  fact  he  states  that  sandstone  and  slate  are  quite 
worthless  for  road-surface  materials,  lasting,  as  they  do,  not  one- 
fifth  as  long  as  trap.  Considering  atmospheric  agencies,  as  well 
as  wear  under  hoofs  and  wheels,  the  rocks  would  stand  about  as 
follows  in  their  proper  order  of  value  as  road-surface  material : 

(1)  Trap,  (2)  syenite,  (3)  granite,  (4)  schist,  (5)  gneiss,  (6) 
limestone,  (7)  quartzite,  (8)  sandstone,  (9)  slate,  (10)  mica  schist, 
(11)  marble. 

While  the  order  of  durability  above  given  applies  to  rock  in  the 
surface  coat  of  a  macadam  road,  it  must  not  be  assumed  that  rocks 


QUARRYING  25 

..    t 

even  low  down  on  the  list  are  not  suitable  for  the  bottom  course  of 
a  macadam  road.  Both  in  the  State  of  New  York  and  in  Massa- 
chusetts it  is  common  to  make  the  lower  course  of  local  stone, 
surfacing  it  with  2  or  3  ins.  of  trap-rock,  and  this  is  usually  good 
practice,  for  the  trap  will  outwear  limestone,  or  any  of  the  softer 
rocks,  several  times  over. 

We  pass  now  to  the  consideration  of  the  form  of  cross-section 
of  the  macadam  itself.  In  Massachusetts  and  New  York  the 
standard  section  is  about  6  ins.  thick  by  12  to  16  ft.  wide,  as  shown 
in  Fig.  1 ;  but  as  above  stated,  the  writer  considers  it  better  prac- 
tice not  to  have  the  shoulders  necessitated  by  this  construction, 
recommending  in  place  thereof  a  crescent  cross-section  of  the 
macadam  shown  in  Fig.  7.  The  advantages  of  this  cross-section 
are  obvious.  The  sub-grade  can  be  surfaced  by  road-scrapers  and 
rolled  its  full  width,  while  the  macadam  tapering  from  nothing  at 
the  edges  to  7  or  8  ins.  at  the  center  has  the  greatest  thickness  at 
the  place  subject  to  the  greatest  wear. 

There  is  the  additional  advantage  that  water  collecting  under 
the  macadam  will  quickly  drain  off  and  not  be  held  by  the  shoul- 
ders. It  may  be  objected  that  wheels  will  .cut  through  the  thin 
crust  at  the  edge,  but  it  is  a  fact  that  even  2  ins.  of  macadam  will 
carry  a  heavy  load  if  the  sub-soil  is  not  watersoaked,  and  no 
danger  of  cutting  need  be  apprehended,  since  loads  will  come 
upon  the  edge  only  when  teams  turn  out  to  pass  one  another. 


QUARRYING. 

Without  discussing  further  the  details  of  design  that  do  not 
materially  affect  the  cost  of  construction  we  shall  pass  to  the  sub- 
ject of  preparation  of  materials  and  cost  thereof.  The  cost  of 
quarrying  may  be  divided  into:  (1)  Cost  of  stripping;  (2)  drill- 


_..  .  .Mocadam 


FIG.  7. — TYPICAL  CROSS-SECTION  OF  MACADAM  ROAD,  AS  RECOM- 
MENDED BY  THE  AUTHOR. 

ing;  (3)  dynamite;  (4)  sledging  large  pieces  and  throwing  them 
back  from  the  quarry  face. 

Stripping  will  vary  with  the  character  of  soil,  depth  of  cut 
necessary  and  distance  to  which  the  material  must  be  moved ;  the 
cost  thereof  is  to  be  calculated  as  for  earthwork. 


26  MACADAM   ROADS 

DRILLING. — This   should   always  be   done   with   power-drills. 
The  cost  of  operating  is  about  as  follows  per  ten-hour  day: 

1  drill  runner $2.f>0 

1  helper 1 .50 

y%  engineer  on  boiler 1.25 

1-3  ton  soft  coal 75 

Repairs  to  drill  and  hose 1.00 


Total $7.00 

With  a  good  drill  runner,  and  in  rock  that  is  not  very  seamy,  70 
ft.  of  hole  may  be  drilled  per  day  at  a  cost  of  10  cts.  per  ft.,  but  it 
frequently  happens  under  adverse  conditions  that  this  cost  is 
doubled.  We  shall  assume  15  cts.  per  ft.  for  drilling.  The  num- 
ber of  feet  of  hole  drilled  per  cubic  yard  of  rock  varies  as  the 
depth  of  the  lift ;  or  since  the  depth  of  hole  is  about  the  same  as 
the  depth  of  lift  or  face,  we  shall  speak  hereafter  in  terms  of  the 
depth  of  hole.  It  is  a  common  rule  to  space  the  holes  a  distance 
apart  equal  to  their  depth  (s=d)  ;  the  writer,  however,  uses  the 
following  original  formula  for  spacing  holes  in  stratified  rock, 

10 
s  =  —  yd. 

4 

Wherein  s  =  distance  apart,  and  d  =  depth  of  holes. 
Comparative  results  for  various  depths  of  holes  using  the  for- 

10 

mulas,  s  ==  d  and  s  —  -  -  \/d : 
4 

Feet  of  drill  hole  per 
cu.  yd.  of  rock. 
10 

"  s  =  d. 

1.0 

1.7 

0.75 

0.40 

0.20 

While  the  common  rule  (s  =  d)  may  be  a  good  one  in  igneous 
rock,  the  writer  has  found  that  with  limestone,  sandstone,  etc.,  it 
does  npt  produce  as  satisfactory  results  as  does  his  own  formula. 


Depth,  ft. 
d. 

2' 

s  =  —  > 
4 
22 

4 

.    1  1 

6 

072 

8          

0.55 

12 

.   0.36 

CRUSHING  27 

Q 

It  is  evident  from  the  accompanying  table  that  whichever  rule  is 
used  the  cost  of  quarrying  increases  rapidly  as  the  depth  of  hole 
decreases;  whence  it  is  desirable  to  make  the  holes  not  less  than 
6  ft.  deep,  and  they  need  not  be  over  12  ft.  to  15  ft.  deep  to  secure 
economical  results. 

DYNAMITE. — The  amount  of  40%  dynamite  required  per 
cubic  yard  of  rock  excavated  varies  also  with  the  depth  of  hole, 
decreasing  as  the  depth  of  hole  increases.  In  open  cut  work  the 

3 
writer  uses  the  original  formula,  P  =  — ,  in  which  P  is  equal  to 

d 
the  pounds  of  dynamite  required  per  cubic  yard  of  rock. 

With  40%  dynamite  at  15  cts.  per  It),  and  drilling  at  15  cts.  per 
ft.,  we  find  upon  summing  up  that  the  cost  in  cents  per  cubic  yard 
of  rock  excavation,  solid  measure,  using  the  writer's  rules,  is  as 
follows : 

Where  d  (in  ft.) 123468     10     12 

Cost  of  dynamite  per  cu.  yd.  .  26  18  15  13  11  9  8  7 
Cost  of  drilling  per  cu.  yd....  66  32  22  17  10  9  7  6 

Total  cost  per  cu.  yd 92     50     37     30     21     18     15     13 

Having  never  seen  a  rational  and  detailed  explanation  showing 
that  the  cost  of  rock  excavation  varies  inversely  as  the  depth  of 
the  lift  in  the  quarry,  the  writer  has  gone  somewhat  into  detail 
for  the  purpose  of  demonstrating  the  necessity  of  opening  up  a 
quarry  so  as  to  secure  considerable  depth  of  face,  if  it  is  desired 
tt)  move  rock  economically. 

The  formulas  given  are  purely  empirical,  based  upon  experi- 
ence, and  not  upon  the  wave  theory  of  the  effect  of  explosives,  but 
it  is  believed  that  the  formulas  are  rational  in  construction. 

Sledging  and  throwing  the  stone  back  from  the  face  will  cost 
about  15  cts.  per  cu.  yd.,  loose  measure,  for  stratified  rock  where  a 
9  x  15-in.  crusher  is  used.  To  sum  up  the  cost  of  quarrying,  ex- 
clusive of  stripping,  pumping  and  superintendence,  we  find  it  to 
be  about  as  follows:  Drilling  and  dynamite,  21  cts.  per  cu.  yd. 
solid  measure,  or  about  15  cts.  per  cu.  yd.  loose  measure,  allow- 
ance being  made  for  waste,  to  which  adding  15  cts.  for  sledging 
we  have  a  total  of  30  cts.  per  cu.  yd.  loose  measure  for  quarrying. 

CRUSHING.— Under  this  head  we  shall  include  the  cost  of  de- 
livering the  stone  from  the  quarry  to  the  crusher  and  shall  assume 
that  a  good  portable  crusher  having  a  9  x  15-in.  opening  is  used. 


28  MACADAM    ROADS 

The  output  of  such  a  crusher  is  ordinarily  about  60  cu.  yds.  in 
ten  hours,  the  stone  being  measured  loose  in  the  bins  or  wagons 
and  using  a  rotary  screen  having  three  sizes  of  circular  openings, 
namely:  %,  1^4  and  1%  ins.  The  output  of  the  various  sizes  is 
about  as  follows:  y2-in.  stone,  16^  ;  1%-in.,  24%  •  2i/2-in.,  60%; 
total,  100%. 

Using  a  stationary  screen  made  of  bars  %  in.  apart,  the 
writer  has  found  the  screenings  to  be  about  25%  of  the  total. 

In  both  cases  the  jaws  of  the  crusher  were  set  to  crush  fine,  and 
all  material  over  2%  ins.  in  diameter  was  run  through  the  crusher 
a  second  time.  If  the  crusher  is  about  100  ft.  distant  from  the  face 
of  the  quarry  it  will  take  six  men  with  wheelbarrows  to  supply  it 
with  stone,  and  it  need  cost  no  more  if  the  crusher  is  somewhat 
further  away,  provided  dumpcarts  are  used  and  the  stone  dumped 
on  the  platform.  Each  man  will  load  and  deliver  in  wheelbarrows 
about  10  cu.  yds.  of  loose  stone  per  day.  It  will  take  two  active 
men  to  feed  this  60  cu.  yds.  daily  into  the  crusher,  at  a  cost  of  5 
cts.  per  cu.  yd.  for  feeding. 

The  engineer  will  receive  about  $2.50  a  day,  equivalent  to  about 
4  cts.  per  cu.  yd.  One  man  will  be  required  to  help  load  the 
wagons  at  the  bins  at  2%  cts.  per  cu.  yd.,  and  one  man  to  carry 
tools  to  the  blacksmith,  etc.,  will  be  needed  at  2%  cts.  a  cu.  yd. 

A  blacksmith,  sharpening  tools  at  $2.50  a  day,  a  water  boy  at  50 
cts.  and  a  foreman  at  $3.00  per  day  add  another  10  cts.  per  cu.  yd. 
to  the  cost  of  quarrying  and  crushing. 

Summing  up,  we  have  the  total  cost  of  loose  stone  per  cu.  yd. 
in  the  wagons,  with  60  cu.  yds.  daily  output,  as  follows : 

Quarrying  and  sledging $  .30 

Wheeling  to  platform 15 

Feeding  crusher 05 

Engineer    04 

Bin  man  and  tool  man 05 

Foreman,  blacksmith  and  waterboy .10 

2-3  ton  of  coal  at  $2.70 03 

Wear  and  tear  on  plant  and  interest,  $3  day 05 


Total   $  .77 

Delays  from  breakdowns 08 

Stripping,  say  15  cts.,  and  quarry  rent  10  cts 25 

Grand   total..  ..$1.10 


HAULING  AND  SPREADING  29 

0 

While  there  is  no  doubt  that  this  cost  may  be  somewhat  reduced, 
it  can  be  done  only  where  work  is  upon  a  sufficiently  large  scale  to 
warrant  the  use  of  a  stationary  plant  of  greater  size  than  is  ordi- 
narily used  on  roadwork.  Crushed  stone  may  be  brought  from  the 
large  quarries  at  75  cts.  per  cu.  yd.,  and  in  certain  places  where 
the  waste  product  of  a  building  stone  quarry  is  crushed  it  may  be 
bought  for  even  less. 

The  writer  has  seen  many  absurdly  low  estimates  of  the  cost  of 
macadam  roads  made  by  engineers  who  have  based  their  prices  of 
stone  upon  the  prices  charged  by  the  quarrymen  on  the  Hudson 
River,  where  the  work  is  carried  on  quite  differently  from  what  is 
possible  with  a  portable  plant  and  in  a  quarry  with  a  shallow  face. 


FIG.    8. — MACADAM  ROAD  WITH  SHALLOW  DITCHES,  AFTER   WIN- 
TER'S   USE. 

(Showing-  macadam  (12  ins.  x  18  ft.)  road  without  ditches;  earth  shoul- 
ders, 9  ft.  wide;  crown  of  road  only  15  ins.  above  bottom  of  gutter.  Road 
in  perfect  condition  after  severe  winter  and  wet  spring.) 


HAULING. — Bins  should  always  be  erected  to  receive  the 
broken  stone  and  so  avoid  rehandling.  A  wagon  can  readily  be 
loaded  from  a  bin  in  two  to  five  minutes.  Ordinarily  not  more 
than  l1/^  cu.  yds.  can  be  hauled  by  a  team.  The  speed  of  the  team 
going  and  returning  should  average  220  ft.  per  minute.  Allowing 
five  minutes  to  dump  the  load  and  five  minutes  in  loading,  the 
fixed  cost  of  hauling  is  7  cts.  per  cu.  yd.,  to  which  add  %  ct.  per 


30  MACADAM  ROADS 

cu.  yd.  per  100  ft.  of  lead,  or  25  cts.  per  mile  where  team  and 
driver  are  worth  35  cts.  per  hour. 

The  fixed  cost  may  readily  become  greater  than  7  cts.  if  there 
are  any  delays  or  breakdowns  at  the  crusher,  and  it  is  safe  to  say, 
that  after  figuring  the  cost  by  the  rule  just  given,  at  least  W/( 
should  be  added  for  such  contingencies.  It  should  be  borne  in  mind 
also  that  all  the  teams  cannot  be  loaded  at  once  in  the  morning, 
and  furthermore  that  the  length  of  haul  is  continually  changing 
so  that  at  certain  times  teams  are  not  working  to  their  full 
capacity. 

SPREADING. — Two  men  will  dump  and  spread  the  output  of 
the  crusher,  or  30  cu.  yds.  each,  unless  the  specifications  compel 
dumping  on  boards  and  shoveling  the  material  therefrom  into  the 
road,  under  which  conditions  at  least  four  men  will  be  required. 
Shoveling  from  dumping  boards  is  in  the  writer's  opinion  a  use- 
less and  expensive  refinement.  It  is  claimed  that  dumping  a  load 
in  one  spot  on  the  road  results  in  undue  consolidation  at  that 
place,  but  the  writer  has  never  seen  any  evidence  of  such  an  effect 
where  the  spreader  knows  his  business,  and  where  slat-bottom 
wagons  are  used,  for  the  spreader  will  then  not  allow  the  load  to 
fall  all  in  one  place,  but  dump  in  several  small  piles,  since  to  do 
otherwise  would  make  more  work  for  himself.  Where  the  output, 
of  several  crushers  is  daily  placed  upon  the  road  a  Shuart  grader 
may  be  used  to  advantage  for  spreading,  as  the  blade  will  pick  up, 
push  along  and  level  at  least  500  cu.  yds.  per  day,  requiring  a 
team  and  driver  and  one  man  at  a  cost  of  $5,  or  1  ct.  per  cu.  yd., 
and  it  will  cost  1  ct.  more  per  cu.  yd.  to  complete  the  leveling  by 
hand  with  a  potato  hook. 

The  screenings  should  not  be  dumped  directly  upon  the  broken 
stone,  but  placed  in  piles  at  convenient  intervals  along  the  sides  of 
the  road  and  spread  with  shovels  after  the  rolling  has  been  almost 
completed.  One  man  will  spread  about  10  cu.  yds.  of  screenings 
per  ten-hour  day  at  a  cost  of  15  cts.  per  cu.  yd. 

It  should  have  been  stated  above  that  screening  is  necessary  to 
insure  the  even  distribution  of  the  binder  throughout  the  road, 
and  Byrne  errs  when  he  advocates  the  placing  of  unscreened  stone 
upon  a  road.  Had  he  observed  the  way  in  which  the  larger  stones 
in  a  bin  roll  down  and  collect  at  the  lower  end  he  would  have  seen 
the  necessity  of  separating  the  sizes  by  means  of  a  screen  to  insure 
even  distribution. 


ROLLING  AND  SPRINKLING  31 

9 

ROLLING. — Byrne  states  in  his  work  on  "Highway  Construc- 
tion" that  in  England  a  roller  averages  1,000  sq.  yds.  of  3-in.  fin- 
ished course  of  macadam  a  day,  which  is  equivalent  to  85  cu.  yds. 
of  macadam  rolled ;  and  he  cites  one  instance  where  twice  this 
amount  of  limestone  was  compacted,  the  roller  passing  over  it  only 
35  times.  If  an  excess  of  binder  and  water  are  put  on  before  the 
coarse  stone  has  been  consolidated  there  is  no  doubt  that  macadam 
may  be  compacted  in  the  short  time  above  given,  but  the  writer 
does  not  believe  that  a  road  can  be  properly  built  with  so  little 
rolling.  North  states  that  in  one  instance  where  a  6-in.  course  of 
trap  macadam  was  applied  in  making:  repairs  it  took  a  15-ton 
roller  38.2  hrs.  per  1,000  sq.  yds.,  or  about  44  cu.  yds.  was  rolled 
per  ten-hour  day.  In  another  instance  it  took  58.6  hrs.  to  pack  a 
7-in.  macadam,  laid  in  two  courses,  or  33  cu.  yds.  per  ten-hour  day. 
Mr.  Cudworth  states  that  a  3-in.  finished  course  of  trap  was  rolled 
at  a  rate  varying  from  38.4  to  65.4  sq.  yds.  per  hour,  or  an  average 
of  about  40  cu.  yds.  per  ten-hour  day ;  while  Mr.  Foster  states 
that  a  6-in.  finished  course  of  trap  was  rolled  at  the  rate  of  31.4  sq. 
yds.  an  hour,  or  52  cu.  yds.  per  ten-hour  day.  The  writer's  experi- 
ence agrees  very  closely  with  that  of  Mr.  North.  For  trap  work, 
the  writer  has  found  that  about  36  cu.  yds.  of  macadam  can  be 
rolled  a  day  and  about  42  cu.  yds.  where  limestone  is  used.  The 
daily  cost  of  operating  a  steam  roller  is  about  as  follows : 

Engineer $  3.00 

Night  watchman 1 .50 

4-10  ton  anthracite  at  $5.50 2.20 

Oil  and  waste .30 

Interest  and  depreciation 3.00 


Total $10.00 

Interest  and  depreciation,  as  given,  may  seem  high,  but  it  is  a 
common  error  among  civil  engineers  not  to  allow  sufficiently  for 
interest  and  depreciation  of  plant,  because  they  usually  forget 
that  such  a  plant  is  not  in  operation  continuously  throughout  the 
year.  A  contractor  will  seldom  average  more  than  100  working 
days  each  season  with  his  roller,  therefore,  with  interest  at  6'/v' 
and  depreciation  at  6</< ,  the  total  is  12%  of  $2,500,  or  $300.  This 
must  be  distributed  over  100  working  days,  and  not  over  300 
working  days,  as  is  frequently  done. 

We  have  included  no  item  for  water,  as  water  is  usually  drawn 
from  the  sprinkling  tanks,  and  is  charged  under  that  head. 


32  MACADAM     ROADS 

With  a  daily  cost  of  $10  for  rolling  40  en.  yds.  of  macadam, 
which  is  a  fair  average,  we  have  25  cts.  per  en.  yd.  as  the  cost  of 
this  item. 

SPRINKLING. — Sprinkling  is  an  extremely  variable  item  of 
cost,  depending  upon  the  source  of  water  supply  and  the  nature  of 
the  sub-grade.  It  will  require  about  4  cu.  ft.  of  water  per  cu.  yd. 
of  macadam  to  puddle  the  screenings.  The  writer  has  been  com- 
pelled to  use  as  much  as  18  cu.  ft.  of  water  to  puddle  1  cu.  yd.  of 
macadam,  but  this  was  under  the  direction  of  an  engineer  who 
had  water  on  the  brain.  One  man  with  a  good  hand-pump  will 
raise  1,000  cu.  ft.  of  water  16  ft.  high  in  10  hours  into  a  tank  from 
which  it  can  be  drawn  off  into  the  sprinklers. 

If  the  product  of  two  good  portable  crushers  is  going  into  the 
road  it  will  take  about  300  cu.  ft.  of  water  daily  to  puddle  the  ma- 
cadam and  an  equal  amount  to  keep  the  sub-grade  in  compact  con- 
dition, although  in  very  sandy  soil  twice  as  much  water  may  he 
needed.  One  man  will  therefore  pump  enough  water  to  supply  80 
cu.  yds.  of  macadam  and  sub-grade  at  a  cost  of  2  cts.  per  cu.  yd.  of 
macadam.  A  sprinkler  holding  60  cu.  ft.  of  water  is  ordinarily 
used,  which,  at  $4  per  day  for  team,  cart  and  driver,  will  supply 
all  the  water  needed  up  to  a  haul  of  l1/^  mile  from  a  storage  tank. 
A  sprinkler  can  be  loaded  in  10  minutes,  and  with  the  speed  of 
team  at  220  ft.  a  minute,  or  2i/>  miles  an  hour,  it  is  easy  to  estimate 
the  number  of  trips  a  day  and  the  number  of  sprinklers  that  will 
be  needed  (with  varying  lengths  of  haul).  Ordinarily  one  sprink- 
ler is  required  for  each  roller,  so  that  the  cost  of  sprinkling  will 
be  10  cts.  per  cu.  yd.,  which,  added  to  the  pumping,  makes  a  total 
of  12  cts.  per  cu.  yd.  of  macadam,  but  with  a  long  haul  and  in 
sandy  soil  the  cost  frequently  runs  as  high  as  20  cts.  per  cu.  yd. 

QUANTITY  OF  MATERIALS  AND  COST  OP  WORK.-As 
stated  above,  6  ins.  of  loose  broken  stone  will  compact  under  the 
roller  to  about  4%  ins.  in  thickness,  or  1.3  cu.  yds.  will  roll  to  1  cu. 
yd.,  packed,  and  the  voids  will  be  reduced  from  about  40%  to 
about  22%,  beyond  which  no  amount  of  rolling  with  a  ten-ton 
steam-roller  will  effect  further  consolidation.  This  data  is  based 
upon  careful  measurement  of  loose  stone  in  the  wagons  and  after- 
wards compacted  into  a  macadam  road  several  miles  along1.  To 
fill  the  voids  in  the  compacted  stone  0.3  cu.  yd.  of  screening  (J/2-in. 
diameter  down  to  dust)  were  required  per  cubic  yard  of  com- 
pacted macadam. 


QUANTITY    AND    COST  33 

• 

It  might  seem  at  first  sight  that  about  0.22  cu.  yd.  of  screenings 
would  be  needed  to  fill  the  voids,  but  an  excess  must  be  provided, 
for  the  puddling  action  of  the  water  used  in  sprinkling,  and  the 
crushing  action  of  the  roller  reduces  the  volume  of  the  loose 
screenings  not  less  than  30%.  The  writer  uses  this  rule,  based 
upon  his  experience :  To  ascertain  the  thickness  of  the  coat  of 
screenings,  multiply  the  thickness  of  the  finished  macadam  by  0.25 
and  add  1-3  in.  to  provide  for  filling  the  surface  voids  and  for  loss. 
This  rule  will  be  found  very  accurate  for  any  thickness  of  macad- 
am from  2  to  12  ins. 

To  sum  up:  It  requires  the  following  amount  of  materials  to 
make  a  6-in.  macadam  road,  properly  rolled  and  with  voids*  re- 
duced to  about  4%. 

1.3  cu.  yds.  of  ~y<2  to  21/o-in.  loose  stone, 

0.3  "     "     "   M}-in-  and  less  screenings, 

1.6  "     "     "   total  loose  stone  to  make  1  cu.  yd.  macadam, 
Or,  stated  differently: 

7.8  ins.  of  loose  stone  %  to  2%  ins.  in  diameter  will  roll  to  6  ins. 
1.8  "     "     "     screenings  will  fill  the  voids. 

9.6  "    •  "     "     stone   and  screenings  will  make   6   ins.   of  ma- 
cadam. 

The  reports  of  the  Massachusetts  Highway  Commission  will  be 
found  to  confirm  this  data,  although  their  unit  of  measurement  is 
the  ton  of  2,000  Ibs.,  and  some  assumptions  must  be  made  to  re- 
duce to  our  unit  of  cubic  yards.  We  shall  assume  that  1  cu.  yd.  of 
trap-rock  weighs  11-3  short  tons.  From  the  report  of  1897  it  may 
be  shown  that  0.336  short  tons  of  stone  and  screenings  were  re- 
quired per  square  yard  of  finished  macadam  averaging  5%  ins. 
thick,  or  about  1.7  cu.  yd.  of  loose  stone  and  screenings  were  re- 
quired per  cubic  yard  of  macadam.  The  report  of  1899  shows  that 
0.328  tons  were  required  per  square  yard  of  macadam,  or  1.62  cu. 
yd.  of  loose  stone  and  screenings  per  cu.  yd.  of  macadam. 

These  figures  are  the  average  of  thousands  of  square  yards  of 
macadam  road.  It  should  be  stated  that  in  a  sandy  roadbed  or 
one  not  perfectly  compacted  by  the  roller,  %  to  1  in.  of  stone  will 
be  pushed  into  the  sub-grade  and  lost,  and  if  a  cushion  coat  of 
screenings  is  specified,  that  also  must  be  added  to  the  above  esti- 


*Coddrington,    In    the    "Encyclopedia    Brittanica,"    states    that    voids    in 
well-compacted  macadam  are  5  per  cent,  as  determined  by  actual  weight. 


34  MACADAM     ROADS 

mated  quantities.  A  cushion  coat  is  entirely  unnecessary,  except 
to  prevent  raveling  in  dry  weather,  and  it  is  then  much  cheaper  to 
use  sand  for  this  purpose. 

According  to  the  present  New  York  State  specifications  all  the 
product  of  the  crusher  from  %  to  1*4  ins.  in  size,  or  25%  of  the 
total  output,  is  wasted,  since  the  specifications  prohibit  its  use. 
This  is  another  of  the  many  absurd  extravagances  to  be  found  in 
so-called  "standard  specifications."  while  it  does  not  produce  a 
better  road,  it  adds  very  materially  to  the  cost  of  roadwork  where 
the  contractor  can  find  no  market  for  stone  of  the  prohibited  sixe. 
We  are  now  in  position  to  estimate  the  cost  of  a  cubic  yard  of 
macadam  in  place,  and,  assuming  the  rates  above  given  and  that 
the  full  product  of  the  crusher  is  used,  find  it  to  be  as  follows : 

1.3  cu.  yds.  coarse  stone  at  $1.10. $1.4:5 

1.3  "       "       "         "       hauled  1  mile  at  32  cts 42 

1.3*'       "       "         "       spread  at  5  cts 06 

1.3"       "       "         "       rolled  at  20  cts 26 

0.3  "       "     screenings  at  $1.10 33 

0.3  "       "  hauled  1  mile  at  32  cts 10 

0.3  "       "  spread  at  15  cts 05 

Sprinkling   12 

Total,  per  cu.  yd.  macadam $2.77 

This  is  for  a  haul  of  one  mile,  and  40  cts.  per  cu.  yd.  of  macadam 
must  be  added  for  each  additional  mile  haul.  As  above  stated,  the 
amount  of  screenings  will  be  slightly  less  than  is  necessary  to  bind 
the  road,  but  it  is  assumed  that  a  small  amount  of  sand  will  be 
allowed  to  piece  out;  should  this  be  prohibited  by  the  specifica- 
tions, screenings  will  have  to  be  imported  at  an  additional  cost. 

The  1899  report  of  the  Massachusetts  Highway  Commission 
shows  that  the  average  contract  price  for  broken  stone  in  place 
was  $1.55  per  ton,  or  about  $3.40  per  cu.  yd.  of  macadam  in  place 
during  1898. 

It  may  be  well  at  this  point  to  insert,  for  sake  of  comparison, 
the  cost  per  mile  of  standard  road,  15  ft.  wide,  6  ins.  thick  at  the 
center  and  5  ins.  on  the  sides,  as  constructed  in  the  state  of  Massa- 
chusetts, where  175  miles  of  road  have  been  built  from  1894  to 
1899. 

The  average  cost  has  been  about  $10,000  per  mile  of  road  and 
the  approximate  per  cent,  of  each  item  is  as  follows ; 


QUANTITY  AND  COST  35 

• 

Per  cent,  of 
total  cost. 
Macadam,  at  $1.50  ton  for  local  stone,  $2.00  ton 

for  trap 55.0 

Excavation  at  32  cts.  cu.  yd.  for  earth  and  $1.50 

for  rock 14.0 

Engineering 12.0 

Culverts  at  $100  each  and  bridge  at  $1,000  each.  .        6.0 

Gravel  for  shoulders  at  60  cts.  cu.  yd 5.0 

Shaping  or  surfacing  at  2  cts.  sq.  yd 2.0 

Side  drains  at  29  cts.  lin.  ft 2.0 

Stone  bounds  and  miscl 2.0 

Guard-rail  at  13  cts.  lin.  ft 1.5 

Telford  bottoming,  at  31  cts.  sq.  yd 0.5 


Total 100.0 

The  most  striking  fact  brought  out  by  this  tabulation  is  that  the 
macadam  itself  has  cost  little  more  than  half  the  total,  while  the 
engineering  alone  has  been  12%  and  the  earthwork  14%,  with 
sundry  items  forming  the  balance.  What  shall  be  said  of  such 
road  construction  ?  However  excellent  it  may  be  in  point  of  artis- 
tic finish  and  utility,  a  road  built  at  such  a  cost  indicates  an  ex- 
travagance that  would  not  be  tolerated  by  a  private  corporation 
just  entering  upon  the  construction  of  good  roads.  The  item  of 
earthwork  is  excessive,  both  as  to  quantity  of  earth  moved  and  as 
to  cost  per  cubic  yard ;  but  we  shall  not  here  repeat  the  criticism 
made  in  Chapter  II.  of  the  design  of  road  cross-section  that  has 
caused  so  great  an  increase  in  this  item. 

The  item  of  shaping,  as  we  have  shown,  is  likewise  greatly  in  ex- 
cess, of  what  it  would  be  were  the  use  of  graders  possible.  Culverts 
and  bridges  should  ordinarily  cost  not  half  as  much  per  mile  of 
road  as  above  given;  while  guard-rails  of  the  expensive  design 
specified  are  uncalled  for  on  a  new  road,  and  as  a  matter  of  fact 
guard-rails  are  generally  quite  unnecessary,  for  while  a  driver 
might  occasionally  go  over  an  embankment,  were  the  horse  pos- 
sessed of  no  intelligence,  the  latter  condition  seldom  exists. 

As  to  the  cost  of  engineering  and  inspection,  we  find  this  item 
to  be  about  three  times  as  great  as  it  should  be.  The  writer  is  an 
engineer  and  would  not  knowingly  advise  the  rejection  of  an  en- 
gineer's services  on  the  ground  of  high  cost.  The  fact  is  that  no 
profession  is  so  poorly  paid,  considering  the  brains  and  ability 


36 


MACADAM     ROADS 


represented ;  but  the  man  of  wisdom  will  see  that  if  the  roads  can 
be  built  more  cheaply,  more  roads  will  be  built,  and  the  engineer's 
services  will  be  more  in  demand. 

The  mere  survey,  estimate  and  plans  should  not,  and  usually  do 
not,  cost  over  $50  per  mile ;  while  the  staking  out  of  the  work  need 
not  cost  over  $30  per  mile.  It  is  therefore  evident  that  inspection 
forms  the  greatest  portion  of  the  engineering  item,  and  this  is  in 
consequence  of  the  slow  progress  made  by  a  contractor  with  a 
small  and  inadequate  plant. 

The  contractor  should  be  required  to  build  one  mile  of  road  a 
month,  once  he  has  installed  his  crushing  plant  and  got  his  quarry 
stripped  and  ready  to  operate,  a  reasonable  allowance  always  be- 
ing made  in  case  of  bad  weather.  With  an  engineer  at  $5  a  day 
and  a  helper  at  $3  a  day  the  cost  would  then  be  about  $250  per 
mile  of  road  for  inspection,  or  a  total  cost  of  $330  for  survey  and 
inspection ;  but  since  the  engineer  and  helper  cannot  work  contin- 


FIG.   9.— ANOTHER   EXAMPLE  OF  SHALLOW  DITCHES. 
(Showing  macadam   (6  ins.  x  16  ft.)   road;  no  ditches;  earth  shoulders  5 
ft.   wide;  crown   9  ins.  above  gutter.     Macadam  perfect  after  severe  winter 
and  wet   spring-.) 

' "        *PL  - 

ually,  and  yet  should  not  be  laid  off  or  dismissed  between  time,  it 
is  safe  to  say  that  engineering  and  inspection  will  cost  $500  per 
mile. 


MACADAM    ROADS  37 

§ 

By  way  of  comparison  we  shall  here  give  the.  cost  of  a  mile  of 
road  built  according  to  Fig.  7,  with  all  unnecessary  items  ex- 
cluded. 

3,000  cu.  yds.  earth  excavation  at  $0.20 $    600 

1,500  cu.  yds.  macadam  in  place  at  $3.50 5,250 

Culverts    300 

Miscellaneous   350 

Engineering  and  inspection 500 


Total $7,000 

This  price  is  just  about  two-thirds  what  it  is  costing  the  State 
of  Massachusetts,  but  the  writer  is  not  merely  theorizing,  for  he 
has  constructed  roads  over  bad  country  for  less  money  than  he  has 
named  above  by  rigorously  excluding  all  unnecessary  items,  such 
as  stone-bounds,  cast-iron  pipe,  expensive  little  bridges  and  cul- 
verts, and  by  the  use  of  rational  specifications  and  cross-sections. 
In  regard  to  the  cost  of  engineering  he  can  also  speak  authorita- 
tively, for  he  has  laid  out  more  than  thirty  miles  of  road  himself 
where  the  engineering  and  inspection  have  together  cost  less  than 
6%  of  the  total  cost  of  the  work. 

In  closing  this  discussion  of  costs  the  writer  should  in  justice 
state  that  the  Massachusetts  roads  have  been  built  in  the  worst 
sections  of  the  state  and  in  small  contracts  of  about  two-thirds  of 
a  mile  in  length  at  a  time,  both  of  which  tend  to  increase  the  cost 
of  engineering  and  other  items.  Economy  in  construction  depends 
very  largely  upon  the  length  of  road  to  be  built,  for  it  costs  as 
much  to  move  and  set  up  a  plant  to  do  half  a  mile  of  road  build- 
ing as  for  two  miles.  The  fixed  cost  of  opening  a  quarry  and  get- 
ting roads  in  shape  over  which  to  haul  is  likewise  almost  as  great 
for  a  small  piece  of  work  as  for  a  larger  piece.  To  build  roads 
economically  it  is  therefore  necessary  to  construct  several  miles  at 
a  stretch,  and  it  is  also  necessary  to  build  several  thousand  dollars 
worth  of  roads  each  year  in  each  state,  for  thus  only  can  contract- 
ors afford  to  provide  themselves  with  adequate  plant  and  tools 
with  which  to  do  the  work  cheaply. 

A  road-construction  plant  is  more  expensive  than  is  generally 
known,  the  cost  of  a  complete  porta'ble  plant  being  about  $7,000, 
distributed  as  follows : 


38  TELFORD    ROADS 

1  crusher,  9  x  15  ins.,  with  rotary  screen $1,000 

Portable  bins 200 

1   15-HP.  engine 200 

1  20-HP;  boiler 600 

12  wheel  scrapers 500 

12  drag  scrapers,  shovels  and  picks 100 

2  Shuart  graders 100 

2  steam  drills 500 

1  5-HP.  boiler  for  drills 400 

Water  and  steam-pipes,  quarry  tools,  etc .* .  .  300 

2  sprinkling  wagons 500 

1  10-ton  steam-roller.  .  2,500 


Total $6,900 

Due  to  the  fact  that  few  towns  can  afford  such  a  plant,  they  en- 
deavor to  get  along  with  the  crusher  alone,  with  the  result  that 
they  neglect  proper  grading,  do  no  rolling  of  sub-grade  at  all  and 
waste  half  their  stone  by  its  becoming  mixed  with  earth ;  use  field 
stone,  often  rotten  to  begin  with,  because  they  cannot  afford 
steam-drills  and  quarrying  plant ;  have  a  portable  crusher  and  no 
bins,  thereby  rehandling  their  stone;  and  finally,  which  is  the 
worst  of  all,  they  possess  no  steam-roller,  without  which  it  is  im- 
possible to  secure  economic  road  construction. 

So  much  twaddle  has  been  published  about  the  desirability  of 
each  township  or  village  owning  a  crusher  that  there  are  scores  of 
crushers  to  each  steam-roller  in  the  State  of  New  York,  whereas 
there  should  be  one  roller  to  every  crusher. 

We  pass  now  to  a  brief  consideration  of  a  type  of  road  formerly 
very  popular  and  still  adapted  to  special  conditions. 


Chapter  V. 
TELFORD  ROADS. 

A  Telford  pavement  consists  of  an  underpinning  or  bottoming 
of  large  stone,  usually  not  less  than  6  ins.  nor  more  than  12  ins. 
deep,  set  on  edge  like  a  rough  block  pavement  and  supporting  a 
layer  of  macadam  or  broken  stone. 

Telford  seems  to  be  especially  adapted  to  wet  soils,  not  easily 
drained,  where  small  broken  stone  would  be  pushed  down  into  the 
soft  soil,  becoming  mixed  therewith.  Wherever  a  cut  is  made, 


TELI^ORD 

• 

especially  where  the  grade  is  fiat  and  in  a  clay  soil,  or  one  of 
quicksand  nature,  it  is  always  advisable  to  use  the  telford construc- 
tion instead  of  macadam,  for  the  large  underpinning  stone  form 
an  excellent  drain  and  one  that  does  not  easily  clog  up,  like  pipes 
or  side  ditches,  in  freezing  weather. 

In  the  writer's  estimation  telford  is  far  preferable  to  macadam; 
also,  in  city  or  village  streets  where  side  ditches  cannot  be  built 
and  where  in  consequence  there  is  usually  an  amount  of  ground 
water  in  the  soil  directly  under  the  pavement  sufficient  in  most 
cases  to  keep  the  sub-grade  in  a  more  or  less  yielding  condition. 
In  Rochester,  N.  Y.,  a  telford  pavement,  consisting  of  an  under- 
pinning 10  ins.  deep,  of  local  limestone  or  sandstone,  surfaced  with 
4  ins.  of  broken  trap-rock,  costs  about  $1.25  per  sq.  yd.,  and  is  a 
pavement  that  is  becoming  deservedly  popular.  There  are,  never- 
theless, many  side  streets  where  a  6-in.  course  of  macadam  alone 
would  be  about  half  as  expensive  and  equally  as  satisfactory, 
where  the  teaming  is  not  heavy.  It  has  been  stated  in  a  widely 
read  pamphlet  on  roads  and  pavements  that  neither  macadam  nor 
telford  is  an  economic  pavement  for  the  streets  of  a  village  or  city. 
The  reasons  cited  in  support  of  this  statement  are  purely  theoret- 
ical and  based  upon  insufficient  data  to  warrant  so  sweeping  a  con- 
clusion, for  not  only  in  the  city  of  Rochester,  but  in  scores  of  other 
cities,  are  to  be  found  most  excellent  examples  of  street  pavements 
made  of  broken  stone.  There  are,  it  is  true,  many  macadam  pave- 
ments that  have  gone  to  pieces  under  heavy  traffic,  but  the  same 
may  be  said  of  brick  and  of  asphalt  where  improperly  constructed 
or  where  poor  materials  have  been  used.  The  telford  construction 
may  be  used  to  advantage  where  a  crusher  is  not  available,  broken 
stone  being  imported  for  the  surface  coat  and  local  stone  used  for 
the  underpinning.  As  to  the  cost  of  a  telford  pavement,  the  under- 
pinning will  usually  cost  about  70  cts.  per  cu.  yd.  corded  up  in  the 
quarry  and  will  shrink  in  laying  about  20%,  bringing  the  cost  for 
the  stone  alone  to  85  cts.  per  cu.  yd.,  to  which  must  be  added  about 
25  cts.  per  mile  for  hauling,  and  25  cts.  per  cu.  yd.  for  laying,  mak- 
ing a  total  of  $1.35  where  the  haul  is  one  mile.  To  this  add  10% 
for  foreman  and  15%)  for  contractor's  profits,  giving  a  total  of 
$1.70  per  cu.  yd.  in  place.  Where  the  haul  is  two  miles  the  cost 
will  be  about  $2  per  cu.  yd.,  or  about  33  cts.  per  sq.  yd.,  for  a  6-in. 
course  of  such  underpinning. 

The  average  price  paid  in  Massachusetts  in  1898  for  some  10,000 
sq.  yds.,  6  ins.  thick,  was  31  cts.  per  sq.  yd.  for  this  underpinning 
or  bottoming.  It  is  to  be  observed  that  a  6-in.  course  of  under- 


40  REPAIRS   AND   MAINTENANCE 

pinning  can  be  put  in  just  as  cheaply  as  a  4-in.  course  of  macadam, 
with  a  haul  of  two  miles.  A  telford  road  is  therefore  not  as  ex- 
pensive as  might  seem  at  first  sight. 


Chapter  VI. 
REPAIRS   AND   MAINTENANCE. 

CONTINUOUS  VS.  INTERMITTENT  SYSTEM.— While  Eng- 
lish and  French  authorities  on  road  construction  advocate  the  con- 
tinuous system  of  repairing  as  being  more  economical  than  the  in- 
termittent system,  the  fact  that  conditions  under  which  we  work 
may  be  different  from  those  from  which  their  experience  was 
gained, — due  measurably  to  the  use  of  rock-crushers  and  steam- 
rollers,— certainly  leaves  the  question  an  open  one. 

The  intermittent  system  prevailing  abroad  seems  to  consist  in 
loosening  the  old  crust  of  a  road,  which  has  been  allowed  to  be- 
come badly  rutted,  with  hand  picks,  and  then  spreading  over  a 
thin  layer  of  new  metal  which  is  rolled  until  bound.  It  is  safe  to 
assume,  in  the  absence  of  cost  data,  that  this  method  is  an  unduly 
expensive  one  to  employ. 

The  following  data,  taken  from  the  author's  time-books,  give 
the  actual  cost  of  resurfacing  a  macadam  road  over  a  mile  in 
length.  While  the  road  was  worn  unevenly,  but  little  new  metal 
(hard  limestone)  was  needed. 

A  12-ton  Buffalo  Pitts  roller  was  used,  which  was  provided  with 
steel  picks  on  the  rear  wheels,  and  80  hours  of  rolling  were  re- 
quired to  break  up  19,400  sq.  yds.  (240  sq.  yds.  per  hour)  of  the 
crust,  which  wras  exceedingly  hard.  The  picks  simply  opened  up 
cracks  in  the  crust  to  a  depth  of  about  4  ins.  and  it  was  necessary 
to  follow  the  roller  with  a  gang  of  laborers  with  hand-picks  to 
complete  the  loosening  process.  The  labor  of  loosening  and  spread- 
ing anew  the  metal  was  slightly  in  excess  of  10  sq.  yds.  per  man- 
hour,  40%  of  which  labor  was  used  in  respreading  with  shovels 
and  potato  hooks. 

After  respreading,  a  short  section  was  so  thoroughly  drenched 
by  a  sprinkling  cart,  that  when  the  roller  came  upon  the  metal, 
the  screenings,  which  had  settled  to  the  bottom  during  the  spread- 
ing process,  were  floated  up  into  the  interstices.  The  roller  and 
sprinkler  were  in  use  but  63  hours,  or  300  sq.  yds.  per  hour.  This 
rapid  rate  was  due  to  the  large  amount  of  water  used  (the  water 
haul  being  short),  the  unyielding  telford  foundation  beneath,  the 


SANDSTONE    MACADAM  41 

Jj 

abundance  of  screenings  and  fine  dust,  and  the  use  of  a  heavy 
roller  operated  at  a  high  speed.  Summing  up,  the  costs  are  seen 
to  have  been  as  follows : 

Cts.  per  sq.  yd. 

Picking  with  roller  at  $1.00  per  hour 0.4 

Picking  by  hand  labor  at  20  cts.  per  hour 1.2 

Respreading  with  roller  at  $1.00  per  hour 0.8 

Rolling  with  roller  at  $1.00  per  hour 0.33 

Sprinkling  with  cart  at  40  cts.  per  hour 0.13 

Foreman,  143  hours  at  30  cts.,  for  19,400  sq.  yds.  .  .  .  0.44 


Total 3.30 

At  this  rate  a  country  macadam  road  16  ft.  wide  can  be  resur- 
faced for  little  more  than  $300  per  mile,  and,  if  built  of  hard  lime- 
stone, will  last  on  the  average  for  five  years. 

It  is  difficult  to  see  how  any  system  of  continuous  repair,  with 
the  inefficient  methods  necessarily  employed,  can  be  as  economical 
as  work  done  in  the  manner  above  described.  It  should  not  be 
understood,  however,  that  an  entire  neglect  of  roads  between  re- 
pair periods  is  favored,  for,  at  times  of  heavy  rains  and  snows, 
ditches  and  culverts  require  attention,  and  there  should  always  be 
someone  whose  duty  it  is  to  look  after  such  matters. 

SANDSTONE  MACADAM.— Sandstone  has  usually  been  pro- 
nounced by  authorities  on  highway  construction  to  be  unfit  for 
road  surfacing.  It  has,  however,  been  successfully  employed  for 
that  purpose  in  Albion,  N.  Y.,  a  city  of  5,000  inhabitants,  and  the 
experience  there  gained  may  be  a  valuable  guide  to  others. 

The  average  width  of  the  residence  streets  between  curbs  is 
about  28  ft. ;  of  this,  18  ft.  is  paved  with  6  or  8  ins.  of  sandstone 
macadam,  leaving  a  5-ft.  earth  shoulder  and  gutter  on  each  side. 

A  very  sharp  crown  is  used,  about  1-in.  per  ft.,  or  a  center  rise 
of  14  ins.  above  the  gutter  in  a  street  28  ft.  wide.  After  a  heavy 
rainfall  the  earth  gutters  become  covered  with  a  thin  layer  of  fine 
materials  evidently  washed  off  the  macadam.  Hitherto  the  author 
has  advocated  a  rather  flat  crown,  about  %  in-  per  ft.,  in  order  not 
to  concentrate  the  traffic  at  the  center  of  the  road.  But  in  a  village 
street,  especially  if  the  macadam  is  of  stone  that  wears  rapidly,  it 
is  evidently  far  preferable  to  resurface  the  street  more  frequently 
as  a  consequence  of  giving  it  a  sharp  crown,  than  to  have  a  dusty 


42  REPAIRS    AND    MAINTENANCE 

or  muddy  street,  which,  costing  considerable  to  keep  clean  by  hoe- 
ing, is  generally  left  until  it  becomes  positively  unbearable.  It  is 
true  that  the  material  washed  by  rains  into  gutters  must  eventual- 
ly be  removed,  but  this  is  much  more  cheaply  done  at  long  inter- 
vals when  greater  quantities  are  to  be  handled.  Moreover,  since 
the  gutters  in  question  are  of  earth,  a  Shuart  or  other  leveling 
scraper  can  be  used  to  gather  up  the  detritus  and  deposit  it  in 
piles  for  removal;  whereas  such  a  scraper  loosens  the  surface  of  a 
macadam  road -and  should  not  be  used  for  cleaning  macadam. 

On  country  roads  made  of  hard  rock  and  swept  by  winds,  a  flat 
crown  is  desirable,  but  where  the  conditions  are  as  in  Albion,  a 
very  sharp  crown  is  evidently  to  be  preferred. 

Medina  sandstone  by  the  rattler  test  has  a  coefficient  of  wear 
about  the  same  as  Rockland  Lake  trap,  whence  it  might  be  infer- 
red that  they  would  exhibit  practically  equal  wearing  qualities  in 
a  road.  There  is,  however,  a  much  greater  uniformity  of  hardness 
in  trap,  which  insures  a  more  even  surface  wear  under  traffic  than 
is  to  be  found  in  sandstone,  which,  like  brick,  appears  to  give  way 
in  spots  that  rapidly  grow  larger.  The  rattler  test  fails  to  show 
one  great  source  of  wear  in  a  road,  namely :  the  crushing  of  loose 
fragments  that,  having  been  picked  out  by  horses'  calks,  are 
ground  to  powder  under  passing  wheels.  This  source  of  wear  is 
greatest  where  the  binding  quality  of  the  rock  is  least,  thus  plac- 
ing a  hard  rock  like  trap  more  nearly  on  a  par  with  a  soft  lime- 
stone than  the  rattler  test  would  indicate.  Whatever  laboratory 
tests  may  show,  it  is  certain  that  the  Medina  sandstone  on  the 
main  street  of  Albion,  under  a  heavy  traffic,  has  lasted  5  years 
without  resurfacing,  and  is  only  (at  the  time  of  observation)  just 
reaching  an  uneven  condition  that  renders  resurfacing  necessary. 
Several  of  the  residence  streets  are  still  in  excellent  condition 
after  5  years'  wear. 

In  this  connection  it  is  well  to  remember  that  because  trap-rock 
wears  twice  as  long  as  limestone,  for  example,  it  by  no  means  fol- 
lows that  it  will  pay  to  use  trap  even  if  it  costs  double  what  lime- 
stone does,  as  the  following  table  clearly  shows: 

Annual  charge  per  sq.  yd.  in  cts. 
Annual     Interest  New  ma- 
Material,  wear.         at  5%     terial.  Total. 

6-in.  limestone  macadam 0.5  in.  1.5  2.5  4.0 

6-in.,  trap  macadam 0.1  in.  3.0  1.0  4.0 

2-in.  limestone  macadam 0.3  in.  0.5  1.5  2.0 

2-in.  trap  macadam 0.1  in.  1.0  1.0  2.0 


REPAIRS    AND    MAINTENANCE  43 

9 

Note. — Limestone  macadam  assumed  at  $1.80  per  cu.  yd., — trap 
macadam  at  $3.60  per  cu.  yd. 

From  the  table  it  is  evident  that  in  a  6-in.  road,  limestone  may 
wear  five  times  faster  than  trap,  prices  being  as  given,  and  yet  be 
no  more  expensive  annually;  while  if  a  2-in.  surface  coat  is  used, 
limestone  must  wear  more  than  three  times  faster  than  trap  to  be 
less  economical,  at  the  cost  and  rate  per  cent,  assumed. 

In  the  method  of  construction  employed  in  Albion  no  attempt  is 
made  to  grade  to  any  established  line.  Mud-holes  are  cleaned  out 
and  stone  thrown  in  to  fill  up  to  the  general  sub-grade  level  (as  a 
general  proposition,  hard  earth  crusts, — the  product  of  years  of 
rolling  and  compacting  by  wagon  wheels, — should  not  be  broken 
up  merely  for  the  sake  of  securing  a  uniform  grade).  The  sand- 
stone is  then  rolled  with  a  15-ton  roller,  and(  being  hand-broken 
stone  containing  no  screenings,  is  more  or  less  broken  into  smaller 
fragments  by  the  roller.  When  rolled  solid  enough  to  support  a 
wide-tired  wagon  without  displacement  of  the  rolled  stone,  wag- 
ons loaded  with  sand  and  loam  are  driven  on.  These  are  spread 
with  shovels  in  a  thin  layer  and  washed  down  into  the  voids  with 
a  sprinkling  cart  or  hose.  After  the  surface  is  dry  enough  so  that 
it  will  not  stick  to  the  wheels,  it  is  again  rolled.  Spreading  of 
sand,  puddling  and  rolling  are  repeated  once  more  before  the  sur- 
face is  satisfactory. 

In  resurfacing,  a  heavy  harrow,  similar  to  those  used  on  farms, 
is  employed  for  completing  the  loosening  of  the  macadam  after  it 
has  been  cracked  open  by  the  spikes  in  the  rear  roller  wheels.  This 
is  constructed  from  4-ins.  x  5-ins.  oak  pieces,  5  ft.  6  ins.  in  length, 
provided  with  pointed  iron  teeth,  1-in.  in  diameter,  and  spaced 
about  10  in.  apart ;  these  teeth  project  about  6  ins.  below  the  wood- 
en frame.  This  harrowing  process  not  only  completes  the  break- 
ing up  of  the  crust  as  well  as  it  could  be  done  by  men  using  picks, 
but  in  addition  the  teeth  spread  the  loosened  stone,  filling  up  the 
low  places. 

The  total  cost  of  resurfacing  is  given  in  the  following  table,  and 
is  considerably  under  the  figures  given  at  the  beginning  of  the 
chapter : 

Cts.  per  sq.  yd. 

Roller  and  engineer  at  $1  per  hour,  picking 0.5 

Roller  and  engineer  at  $1  per  hour,  re-rolling 0.5 

Sprinkling  with  cart,  40  cts.  per  hour 0.2 

Harrowing  with  team  and  driver,  30  cts.  per  hour.  .    0.3 


Total..  1.5 


44  ROAD   SPECIFICATIONS 

At  this  rate  a  macadam  road  16  ft.  wide  and  a  mile  long  can  be 
resurfaced  for  less  than  $140,  or  about  one-half  the  cost  cited 
earlier,  less  than  $30  per  mile  per  annum.  In  addition  to  this  labor 
cost  some  75  cu.  yds.  of  stone  are  required  which  cost  a  trifle  over 
$60,  delivered  and  spread,  making-  a  total  of  $90  per  mile  per  an- 
num for  labor  and  material  for  resurfacing  a  Medina  sandstone 
road.  This  particular  stretch  of  road  was  a  main-traveled  street 
and  the  loss  by  wear  was  even  less  than  the  amount  of  new  metal 
used  in  repairing, — about  0.2  in.  per  annum  over  the  whole  sur- 
face. 


Chapter  VII. 

SUGGESTED  IMPROVEMENTS  IN  EXISTING  ROAD  SPECI- 
FICATIONS. 

The  author  would  call  particular  attention  to  certain  clauses  in 
the  "standard  specifications"  for  macadam  work  as  exemplified  in 
present  practice  in  the  state  of  New  York  and  Massachusetts, 
which,  in  his  opinion,  are  open  to  criticism.  The  clauses  to  be 
taken  up  are  quoted  from  the  specifications  for  recent  New  York 
State  roadwork;  equally  indefensible  clauses  are  to  be  found  in 
those  of  Massachusetts. 

The  first  paragraph  is  as  follows : 

KIND  AND  SIZES  OP  BROKEN  STONE. 

•'The  broken  stone  shall  be  of  two  courses.  The  bottom  course 
will  be  4  ins.  thick  and  may  consist  of  trap-rock,  granite  or  any  of 
the  harder  grade  of  limestone  not  inferior  to  the  specimens  exhib- 
ited in  the  offices  of  the  State  Engineer  and  Surveyor  and  of  the 
Engineer  of  the  Western  Division,  which  stone  shall  be  broken  in 
sizes  varying  from  a  minimum  of  1%  ins.  to  a  maximum  of  3  ins. 
in  their  longest  dimensions. 

"The  top  course  shall  be  2  ins.  thick  after  rolling,  and  shall  con- 
sist of  trap-rock  broken  in  sizes  varying  from  a  minimum  of  1  in. 
to  a  maximum  of  2  ins.  in  their  longest  dimensions. 

"Limestone  screenings  not-exceeding  %  in.  in  size  and  free  from 
all  dirt  shall  be  added  to  fill  all  interstices  that  cannot  be  filled  by 
the  rolling  or  compacting  of  the  other  stone.  Such  screenings 
must  be  free  from  earth,  sand,  loam  or  vegetable  matter  and  shall 
contain  all  the  dust  of  fracture." 


ROAD   SPECIFICATIONS  45 

t 

It  will  be  noticed  that  no  provision  is  made  for  the  use  of  the  % 
to  IV-i-in.  sized  product  of  local  stone  in  the  lower  course.  This 
size  of  stone  forms  about  25 %  of  the  crusher  output,  and  its  rejec- 
tion, therefore,  means  an  added  cost  of  33 c/(  per  cu.  yd.  of  product 
that  can  be  used.  That  this  waste  is  entirely  unjustifiable  can  be 
proven  by  the  existence  of  good  roads  where  every  particle  of 
stone  coming-  from  the  crusher  has  been  used. 

Secondly,  it  will  be  seen  in  the  specification  that  the  binder  for 
both  courses  must  be  limestone.  This,  no  doubt,  arises  from  the 
assumption  that  quartz-like  screenings  will  not  bind.  Sandstone 
has,  however,  been  used  in  many  roads  as  a  binder,  and  where  slow 
in  binding,  the  addition  of  a  little  dust,  preferably  limestone, 
quickly  accomplishes  the  desired  end.  Trap-rock  screenings  are 
also  excluded  from  use  by  the  specification.  Since  trap  is  not  a 
local  product,  but  is  shipped  from  the  Palisades  by  boat  or  rail, 
it  might  seem  at  first  sight  that  the  State  incurs  no  loss  in  specify- 
ing limestone  screenings  for  a  binder,  as  Tompkins  Cove  screen- 
ings certainly  bind,  more  quickly  and  cost  but  little  more  than 
trap.  But  on  inspection  it  will  be  seen  that  if  trap  screenings  are 
uniformly  rejected,  the  price  of  the  coarse  trap  must  ultimately  be 
raised  for  the  same  reason  as  above  given  regarding  the  waste  of 
middle-sized  local  stone.  Trap  screenings,  on  account  of  the  small 
amount  of  dust  they  contain,  bind  very  slowly,  and  not  until 
enough  dust  has  been  produced  by  the  grinding  of  the  coarse  stone 
under  the  roller.  This  grinding,  however,  wears  the  coarse  stone 
round,  and  is  therefore  objectionable.  To  cause  trap  screenings 
to  bind  quickly,  simply  add  a  little  dust,  preferably  road-sweep- 
ings or  limestone.  All  difficulty  from  using  trap  screenings  will 
then  vanish,  and  their  use  will  cheapen  road  construction. 

As  to  the  size  of  trap  specified,  the  author  has  been  unable  to 
find  any  quarry  man  on  the  Hudson  who  uses  screens  that  produce 
stone  "not  less  than  1  in.  and  not  more  than  2  ins.  in  diameter." 
This  specification,  however,  is  practically  disregarded,  most  con- 
tractors using  the  "2%-in.  stone,"  ranging  from  2l/±  to  3l/4  in.  in 
diameter,  and  its  use  has  proved  very  satisfactory. 

DEPTH  OF  PAVEMENT. 

"The  pavement,  when  completed,  shall  be  at  least  6  ins.  in  depth, 
irrespective  of  the  surfacing  material,  as  is  required  by  the  speci- 
fications, and  of  such  crown  and  form  of  gutter  as  are  shown  on 
plans ;  and  in  any  case  the  thickness  of  the  pavement  is  to  be  de- 
termined on  a  line  at  right  angles  to  the  grade  and  crown. 


46  ROAD   SPECIFICATIONS 

"NO  ALLOWANCE  WILL  BE  MADE  FOR  ANY  MATERIAL 
DRIVEN  INTO  THE  SUBGRADE  BY  ROLLING  OR  MISTAKE 
MADE  BY  CONTRACTOR  IN  EXCAVATING  OR  FILLING. 

The  use  of  a  proper  roller,  rammers  or  other  suitable  implement  is 
to  be  substituted  for  that  of  the  steam-roller  when  the  engineer  so 
directs. ' ' 

Here  is  seen,  what  is  not  uncommon,  an  effort  to  throw  all  the 
uncertainty  of  cost  upon  the  contractor,  who  must  guess  whether 
there  will  be  1  in.  or  4  ins.  of  stone  driven  into  the  subgrade,  and 
if  his  guess  is  not  correct,  he  must  lose  or  gain  as  the  case  may  be. 
Such  specifications  are  not  only  morally  but  economically  wrong, 
for  the  inexperienced  contractor  is  almost  certain  to  lose  a  just 
compensation  for  work  for  which  the  State  is  able  and  willing  to 
pay,  while  the  experienced  contractor  will  err,  if  at  all,  on  the  side 
of  safety,  and  so  receive  pay  for  material  that  he  will  not  have  to 
furnish. 

This  specification  is,  moreover,  based  upon  a  false  reason,  for  it 
implies  that  all  stone  driven  into  sub-grade  is  lost  and  valueless, 
which  is  not  the  case.  When  stone  is  driven  down,  the  soil  is 
forced  up  into  the  voids,  and  there  results  a  macadam  with  a 
binder  of  sand  or  loam,  which,  if  not  as  good  as  macadam  bound 
with  screenings,  is  nevertheless  capable  of  aiding  in  the  distribu- 
tion of  a  concentrated  wheel  load,  and  therefore  performs  the 
most  important  function  of  a  pavement. 

The  only  fair  way  to  pay  for  macadam  in  thin  roads  is  either  by 
the  ton  or  by  the  cubic  yard  in  the  wagons.  No  effort  should  be 
made  to  finish  a  road  surface  exactly  to  a  predetermined  grade,  as 
is  the  present  practice  in  Massachusetts  and  New  York. 

FINAL  SURFACING. 

"After  the  wave  has  been  produced  over  the  whole  section  of 
the  road,  screenings  shall  be  again  spread  on  where  required  to 
leave  them  %-iii.  deep  for  a  wearing  surface. ' ' 

To  cover  a  16-ft.  road  to  a  depth  of  %  in.  for  a  mile  requires 
about  100  cu.  yds.  of  screenings,  which,  when  imported  by  rail  and 
hauled,  seldom  cost  less  than  $2  a  cu.  yd.,  and  frequently  $3.  Jhus, 
to  provide  a  perfectly  useless  "wearing  surface"  we  find  the  State 
expending  some  $200  to  $300  a  mile.  Any  screenings  ove"r  and 
above  those  needed  to  fill  voids  serve  no  useful  function  upon  a 


ROAD  SPECIFICATIONS  47 

• 

road  except  to  prevent  .horses'  hoofs  from  loosening  the  stones, 
and  to  keep  the  macadam  from  raveling,  for  which  purpose  sand 
or  loam  serves  equally  well. 

MATERIAL  FOR  EMBANKMENTS. 

"Embankments  shall  be  formed  of  clear  earth  or  other  mater- 
ials satisfactory  to  the  engineer,  and  shall  be  free  from  vegetable 
matter  or  refuse  of  any  kind. ' ' 

In  order  to  carry  out  this  provision  2,000  cu.  yds.  of  soil  con- 
taining sod  are  removed  and  wasted  per  mile  of  road,  which  means 
a  waste  of  about  $500  per  mile.  The  roots  of  grass  extend  the  full 
depth  of  a  plow  furrow,  and  their  removal  can  only  be  accom- 
plished by  taking  with  them  the  earth  to  a  depth  of  6  or  8  ins. 
While  sod  may  not  be  desirable  in  a  very  shallow  embankment 
covered  by  macadam,  it  may  to  advantage  be  used  to  form  the 
shoulders  at  the  sides.  Green  grass  and  weeds  may  be  economical- 
ly and  efficiently  removed  by  using  a  mattock  and  taking  off  only 
about  I1/-;  ins.  of  soil  instead  of  6  or  8  ins., — cost  '%  ct.  per  s<|.  yd. 
of  surface,  with  labor  at  15  cts.  per  hour. 

THICKNESS  AND  WIDTH  OF  PAVEMENT. 

The  standard  thickness  of  the  macadam  on  New  York  State 
roads  is  6  ins.,  and  the  width  16  ft.,  with  occasionally  a  12-ft.  road. 
Upon  very  soft  sand  or  clay  subsoil  it  is  necessary  to  have  6  ins.  or 
more  of  pavement,  but  upon  ordinary,  loamy  or  gravelly  soils  4 
ins.  will  suffice.  The  main  function  of  a  pavement  is  not  to  shed 
water,  as  commonly  stated,  but  to  distribute  a  concentrated  wheel 
load  over  a  sufficiently  large  area  of  subsoil  that  will  not  yield  un- 
der pressure.  Incidentally,  the  drier  the  soil  (sand  excepted)  the 
more  resistance  it  gives  to  pressure,  whence  it  is  desirable  to  pro- 
vide a  pavement  that  will  keep  the  subsoil  dry, — a  secondary 
though  important  consideration. 

A  thick  pavement  is  necessary  upon  sand,  and  also  upon  clay 
when  the  latter  is  not  well  drained;  but  this  thickness  should  not 
always  be  obtained  by  the  use  of  expensive  broken  stone,  but  by 
gravel  where  available  at  less  cost.  Thus,  3  to  6  ins.  of  gravel 
should  ordinarily  form  the  lower  course  upon  which  3  or  4  ins.  of 
macadam  should  be  laid  for  a  wearing  coat,  instead  of  the  invari- 
able 6  ins.  of  macadam  prescribed  in  New  York  and  Massa- 
chusetts. 


48  SUMMARY    AND    CONCLUSIONS 

For  several  reasons  the  author  inclines  to  the  opinion  that  a  nar- 
row road  (8-ft.)  would  compare  very  favorably  with  a  wide  (16- 
ft.)  road.  Traffic  follows  the  center  of  a  16-ft.  road  in  any  case, 
and  the  wear  is  practically  as  concentrated  as  on  a  narrower  road, 
while  the  loss  due  to  weathering  is  only  one-half  as  great  upon  an 
8-ft.  road.  One  objection  to  an  8-ft.  road  is  that  two  teams  can- 
not pass  on  it,  but  this  difficulty  is  successfully  disposed  of, — 
where  the  road  is  built  for  the  hauling  of  farm  produce  and  not 
for  a  speedway, — by  providing  turnouts,  40  ft.  long,  every  320  ft. 
These  turnouts,  having  a  width  of  16  ft.,  are  equivalent  to  adding 
1  ft.  of  width  to  the  road,  and  a  9  ft.  macadam  pavement  4  ins. 
thick  would  cost  only  $1,800  a  mile,  with  stone  at  $3.00  per  cu.  yd. 

By  following  the  foregoing  suggestions  it  is  perfectly  feasible 
to  build  good,  serviceable  macadam  roads  in  New  York  State  for 
about  $3,500  a  mile.  They  will  not  be  speedways  upon  which  two 
teams  can  pass  at  a  full  trot,  but  they  will  be  hard,  unyielding 
surfaces  over  which  great  loads  may  be  drawn  in  all  kinds  of 
weather. 


Chapter   VIII. 
SUMMARY  AND  CONCLUSIONS. 

At  the  close  of  a  discussion  it  is  always  well  to  sum  up  the  cer- 
dinal  points  which  have  been  brought  out  in  order  to  impress  upon 
the  mind  conclusions  worthy  of  remembrance,  if  any  there  are. 
In  the  second  chapter  the  fact  was  brought  out  that  economic  road 
construction  has  not  been  the  first  consideration  of  engineers  em- 
ployed by  certain  states,  however  excellent  otherwise  may  have 
been  the  structures  designed  by  them.  It  was  there  shown  that  to 
perform  earthwork  economically  the  engineer  must  understand  the 
efficiency  of  modern  tools  that  can  be  used,  and  so  design  the 
cross-section  of  a  road  as  to  make  such  use  possible. 

We  have  indicated  the  possibility  and  the  desirability  of  reduc- 
ing the  width  of  cuts  by  the  use  of  sub-drain,  and  the  necessity  of 
keeping  the  mouths  of  such  drains  open  after  a  snow. 

We  have  shown  that  deep  cuts  may  be  avoided  by  a  considera- 
tion of  the  fact  that  the  power  of  a  team  is  not  constant,  but  may 
be  as  great  as  1,000  Ibs.  tractive  pull  for  a  short  time, — sufficient 
to  mount  a  grade  of  7%  with  a  net  load  of  four  tons.  We  have 
pointed  out  the  fact  that  the  heaving  action  of  frost  does  not  ma- 
terially affect  a  macadam  road  that  has  a  foot  of  dry  soil  beneath 


SUMMARY 


it,  and  that  the  excessive  depth  of  ditches  so  commonly  seen  is  un- 
called for. 

In  Chapter  III.  attention  was  called  to  the  necessity  of  screen- 
ing all  gravel  that  is  to  be  used  in  road  construction,  in  order  to 
secure  an  even  distribution  of  coarse  and  fine,  as  well  as  to  ex- 
clude an  excess  of  fines. 

It  was  shown  that  large  stone  do  not  work  to  the  surface  of  a 
gravel  or  a  macadam  road  where  a  binder  has  been  used,  and  that 
those  who  assert  that  such  an  action  takes  place  do  so  entirely 
upon  the  authority  of  Macadam,  who  used  no  binder  at  all. 

In  Chapter  IV.  the  endeavor  was  made  to  establish  a  new  theory 
as  to  the  cause  of  the  binding  that  takes  place  when  a  broken 
stone  is  rolled  and  sprinkled  ;  and,  whether  the  theory  that  water 
in  the  capillary  voids  of  the  screenings  is  the  true  binding  agent 
shall  be  found  to  be  a  complete  and  perfect  theory  or  not,  we  have 
at  any  rate  shown  the  necessity  of  having  fine  dust  in  the  screen- 
ings or  binder. 

We  have  indicated  in  detail  the  places  where  the  expenses  of 
constructing  a  macadam  road  may  be  legitimately  reduced,  begin- 
ning with  less  earthwork,  the  use  of  inexpensive  binder,  the  cut- 
ting out  of  many  expensive  culverts,  bridges  and  miscellanies,  and 
finally  ending  with  a  decided  reduction  in  the  cost  of  engineering. 

We  have  suggested  the  construction  of  all  roads  by  contract 
upon  a  scale  sufficiently  large  to  warrant  outlay  for  a  good  plant  ; 
since  a  good  road  at  a  reasonable  price  has  not  been  built  by  a 
state,  town  or  municipality  under  any  other  than  the  contract  sys- 
tem. The  reason  for  this  is  that  each  road  district  or  town  cannot 
usually  afford  the  plant  necessary,  and  even  though  it  could,  the 
efficiency  of  men  working  for  the  public  is  well  known  to  be  far 
below  the  efficiency  of  the  same  men  working  for  an  individual. 
In  Chapter  V.  it  is  pointed  out  that  the  telf  ord  construction  is  not 
as  expensive  as  is  commonly  supposed,  and  that  it  is  particularly 
adapted  for  cuts  and  in  places  where  side  ditches  cannot  be  made, 
or  where  if  made,  are  liable  to  become  clogged  with  snow. 

An  article  upon  road  construction  would  be  incomplete  without 
some  reference  to  the  laws  under  which  roads  are  built.  A  good 
State  law  wherein  the  State  at  large  bears  one-third  the  burden, 
the  town  or  city  or  county  directly  benefited  bearing  also  one- 
third,  the  taxpayers  along  the  line  of  the  road  bearing  the  re- 
mainder, is  probably  the  most  satisfactory  law  under  which  to 
construct  roads.  Thus,  any  farmer,  .who  owns  a  team  and  desires 
work,  can  pay  his  share  of  the  taxes  several  times  over  from  the 


50  £  j/c  V      8T.1MMARY     4N,D(  CONCLUSIONS 

money  he  earns,  securing  all  the  benefits  of  the  old  system  of 
working  out  taxes,  with  none  of  the  ills.  The  great  popularity  of 
such  a  law  is  to  be  found  by  observing  its  operation  in  New  York, 
Massachusetts,  New  Jersey,  Washington  and  other  states.  In 
New  York  State  the  new  law,  but  two  years  old,  has  brought  out 
petitions  for  over  400  miles  of  macadam  road,  which  it  will  take 
four  years  to  complete,  even  with  an  expenditure  of  $1,000.000 
annually,  while  the  object  lesson  given  by  the  construction  of 
these  roads  will  result  in  petitions  for  hundreds  of  miles  more. 

A  good  macadam  road  makes  it  possible  to  reach  market  in  all 
kinds  of  weather  and  at  a  speed  before  unthought  of.  It  brings 
the  city  man  into  the  country,  and  by  creating  a  demand  for  prop- 
erty for  residence  purposes,  greatly  enhances  the  value  of  the 
farms.  A  good  road  makes  possible  the  hauling  of  loads  weighing 
three  to  five  tons,  and  it  reduces  the  wear  and  tear  of  wagons, 
harnesses,  horses  and  men. 

Road  construction  puts  money  into  circulation  where  the  road 
is  being  built,  fully  three-fourths  of  the  money  coming  from  out- 
side sources  and  remaining  in  the  road  district. 

No  farmer  with  a  grain  of  intelligence  will  oppose  road  con- 
struction under  a  good  law  in  the  face  of  all  these  facts ;  and,  to 
the  credit  of  the  shrewdness  of  the  American  farmer,  be  it  said 
that  in  no  community  where  roads  have  been  built  as  described, 
has  the  verdict  been  anything  but  unanimous  in  favor  of  more 
good  roads. 


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